INTRODUCTION — Health care providers are frequently consulted by couples concerned about their fertility potential. Some couples seek this information even before attempting pregnancy or meeting criteria for subfertility. These couples are especially motivated to listen to advice concerning the impact of lifestyle factors on fertility, as well as their general health.
Epidemiologic studies suggest that some lifestyle factors have small, cumulative effects that prolong the duration of time before achieving pregnancy [1]. Conversely, modifications of these factors appear to improve fertility potential, although this has not been evaluated by randomized trials [2-4].
The impact of lifestyle on fertility, and the implications of these findings for a couple planning pregnancy, will be reviewed here. The evaluation and treatment of subfertile couples are discussed separately. (See "Overview of infertility".)
OVERVIEW OF NATURAL FERTILITY — The following discussion reviews basic terminology and questions about the reproductive process.
Terminology — The following terms are used when discussing fertility:
●Fertility (also called fecundity) refers to the capacity to conceive and produce offspring.
●Infertility is a "disease characterized by the failure to establish a clinical pregnancy after 12 months of regular, unprotected sexual intercourse or due to the impairment of a person's capacity to reproduce either as an individual or with his/her partner" [5]. Infertility refers to a state in which the capacity for fertility may be diminished but not necessarily absent. For this reason, the term subfertility is often used instead of infertility. Sterility is the inability to produce offspring.
●Fecundability is the probability of achieving a pregnancy in a single menstrual cycle. Subfecundity is a decrease in fecundability.
●Time to pregnancy refers to the length of time, usually measured in months, that it takes a couple to conceive. This parameter is often used in epidemiological studies as a measure of subfecundity [6,7].
What is normal natural fertility? — Most pregnancies occur during the first six menstrual cycles of attempted conception [7,8]; fecundability decreases as the number of consecutive months without achieving pregnancy increases (figure 1). In the first six months of attempting pregnancy, approximately 80 percent of couples will conceive; in the first 12 months, approximately 85 percent will conceive. Over the next 36 months, approximately 50 percent of remaining couples will go on to conceive spontaneously [9]. The 5 to 7 percent of couples who have not conceived after 48 months of attempted conception will only occasionally go on to achieve a spontaneous conception.
Criteria for initiating an infertility evaluation vary depending on personal characteristics (eg, age) and are discussed separately. (See "Evaluation of female infertility" and "Approach to the male with infertility".)
When is the fertile period of the cycle? — The fertile interval in each cycle is approximately six days and includes the five days prior to ovulation plus the day of ovulation [10]. The duration of the fertile period is not affected by age but can vary among women [11]. The highest probability of conception occurs when intercourse takes place one to two days prior to ovulation and on the day of ovulation [10,12-17]. A novel approach to the issue of coital timing for reproduction involves the use of a mobile application (ie, app). A study of one proprietary app analyzed data from over 200,000 menstrual cycles and nearly 100,000 women to determine the probability of pregnancy in the periovulatory period [18]. The day-specific probability of pregnancy in relation to ovulation was 27, 33, 42, 20, and 8 percent for -3, -2, -1 days prior to ovulation, day of ovulation, and +1 days, respectively. The use of fertility apps to either time or avoid conception is presented in detail elsewhere. (See "Fertility awareness-based methods of pregnancy prevention", section on 'Computer and phone applications (apps)'.)
Women can attempt to predict the time of ovulation by tracking changes in cervical mucus (highest probability of conception is on the day of peak production of slippery clear mucus) or by using a kit to measure urinary luteinizing hormone (LH). Use of a home ovulation test kit may decrease the time to conception [19], particularly in women with irregular cycles or couples who have sexual intercourse infrequently. However, for most women, there is no substantial evidence that self-monitoring to predict ovulation increases cycle fecundability [20,21]. (See "Evaluation of the menstrual cycle and timing of ovulation", section on 'Measurement of LH surge and estradiol rise'.)
What is the optimum coital frequency to achieve conception? — The highest pregnancy rates occur in couples who have intercourse every one to two days [12,22-24], but regular intercourse two to three times per week beginning soon after cessation of menses should ensure that intercourse falls within the fertile period and semen quality is optimal [25]. Most data indicate that optimum semen quality, measured in terms of motility, morphology, and total sperm count, occurs when there are two to three days of ejaculatory abstinence; longer intervals are associated with lower pregnancy rates [26].
Effect of lubricants — Some lubricants inhibit sperm motility in vitro (eg, KY jelly, Astroglide, Touch, Replens, olive oil, saliva, KY Sensitive, KY Warming, KY Tingling) [27-32]; however, a secondary analysis of couples in a prospective time-to-pregnancy study found no difference in fecundability between those who used and did not use lubricants (primarily Astroglide, KY Jelly, or Pre-seed) [33]. Although there are no compelling data to suggest that lubricant use impairs fertility, the use of lubricants that do not inhibit sperm motility, such as mineral oil, canola oil, mustard oil, or hydroxyethylcellulose-base (Pre-Seed), is prudent when lubricants are needed.
Coital factors that do not affect fertility — Coital position, presence or absence of female orgasm, and female position (eg, remaining supine) after male ejaculation do not appear to affect the likelihood of conception [20].
How does age affect fertility? — Delayed childbearing can decrease the probability of successful conception and should be taken into account in family and career planning. Women in their late 30s are approximately 40 percent less fertile than women in their early 20s. (See "Effects of advanced maternal age on pregnancy".)
The probability of conception is highly dependent upon maternal age, but paternal age also plays a minor role, especially after age 50 years [34]. In a large well-designed study, the probability of clinical pregnancy following intercourse on the most fertile day of the cycle in women of assumed fertility aged 19 to 26 years, 27 to 34 years, and 35 to 39 years was approximately 50, 40, and 30 percent, respectively, if the male partner was the same age, but 45, 40, and 15 percent, respectively, if he was five years older [35]. (See "Effect of advanced paternal age on fertility and pregnancy".)
EFFECT OF ENVIRONMENTAL AND LIFESTYLE FACTORS ON FERTILITY — There are no large-scale, randomized, clinical trials examining the effect of lifestyle issues such as cigarette smoking, body mass index (BMI), stress, or alcohol and caffeine consumption on fertility. Most studies are observational and subject to many potential biases. As an example, numerous investigators have reported that primary tubal infertility is increased in women who report a history of many sexual partners, an earlier age at first intercourse, and cigarette smoking. However, women with more sexual partners and an earlier age at first intercourse may also be more likely to smoke cigarettes; thus, it is often difficult to definitively determine if cigarette smoking is an independent contributor to infertility or whether cigarette smoking is largely associated with infertility through other exposures, such as sexually transmitted infections [36,37]. In addition, women who smoke cigarettes tend to consume more alcohol and caffeine than women who do not smoke. This raises the possibility that the relationship between cigarette smoking and reduced fertility may influence observations of an association between alcohol and caffeine consumption and diminished fertility.
In many of the studies discussed below, attempts were made to control for some of the potential confounding interactions through the use of logistic regression and multivariate analyses. However, the absence of data from randomized trials is a major weakness of the evidence in this area. An additional limitation is that there is no biomarker that can be measured to indicate the potential for human conception [38].
Tobacco use — Use of tobacco by the female partner, and possibly by the male partner, has been associated with subfertility, and may account for as much as 13 percent of cases [39]. Observational studies suggest that much of the subfertility associated with smoking can be reversed within a year of cessation [40-43].
Given the multiple health risks associated with cigarette smoking, cessation should be encouraged irrespective of fertility and pregnancy issues. (See "Benefits and consequences of smoking cessation" and "Overview of smoking cessation management in adults".)
Female partner — Studies of the impact of smoking on fertility have typically analyzed the effects of "cigarettes smoked per day" on fecundability. Most series report that fecundability is decreased if the female partner smokes more than 10 cigarettes per day. In a 1998 meta-analysis including data from almost 11,000 smoking women and over 19,000 nonsmokers, cigarette smoking by the female partner was associated with a statistically significant increase in infertility compared with nonsmokers (odds ratio [OR] 1.60, 95% CI 1.34-1.91) [44]. Although only observational studies were included, the evidence was compelling because of the consistency of the effect across different study designs, sample sizes, and types of outcome. Others have reported that the time to achieve pregnancy increases with the number of cigarettes smoked per day (figure 2) [45].
An additional concern is that subfertility in smokers cannot necessarily be overcome by assisted reproductive technology (ART). The same 1998 meta-analysis found that the odds of pregnancy per number of in vitro fertilization (IVF) cycles was significantly lower in smokers compared with nonsmokers (OR 0.66, 95% CI 0.49-0.88) [44].
Possible mechanisms for subfertility in smokers include adverse tubal and/or cervical changes, damage to gametes, and increase in spontaneous abortion and ectopic pregnancies [37,46]. Numerous studies linking smoking to early menopause suggest that cigarette smoking causes premature depletion of the ovarian pool of oocytes and premature aging of the ovary by one to four years [47,48]; this decrease in ovarian reserve can account for the subfertility observed in smokers.
Components of cigarette smoke may cause oxidative stress and DNA damage to the ovarian follicle [49,50]. For this reason, smoking by a pregnant woman may be harmful to the ovaries of her fetus [51]. In a study of the effect of in-utero exposure to cigarette smoke on the fertility of the female partner, fecundability was reduced among women exposed to cigarette smoke in-utero (fecundability ratio 0.5, 95% CI 0.4-0.8) [52]. This association was present after adjusting for age of the female partner, frequency of intercourse, current smoking status, age at menarche, childhood exposure to cigarette smoke, body mass of the female partner, alcohol and caffeine consumption, educational level, and reproductive history. There may also be adverse reproductive effects of maternal smoking on male fetuses. An epidemiologic study reported that adult male offspring of mothers who smoked more than 10 cigarettes/day during pregnancy had lower sperm counts than the sons of nonsmokers [53].
Male partner — Dose-dependent decreases in semen quality have been observed in men who smoke, but available evidence does not prove that smoking decreases male fertility. An analysis of 27 epidemiologic studies addressing the effect of smoking on sperm concentration, motility, and morphology in fertile and infertile men found a modest reduction in semen quality and altered hormone levels among smokers compared with nonsmokers, but did not find a reduction in male fertility associated with paternal smoking [54]. Fertile male smokers had a 23 percent decrease in sperm concentration and a 13 percent decrease in sperm motility compared with fertile male nonsmokers.
A deleterious effect on male fertility or a secondary deleterious effect on female fertility cannot be definitively excluded, especially among men with marginal semen quality. Studies in subfertile populations that evaluated the effect of smoking by the male partner on the success rate of IVF and intracytoplasmic sperm injection (ICSI) have reported a significant decrease in the number of pregnancies achieved [55,56].
Overweight and obesity — Obese and underweight women are at risk of subfertility as well as other adverse effects on health. The offspring of overweight and obese mothers are at increased risk of congenital malformations [57]. The effect of BMI on male fertility is unclear. (See "Overweight and obesity in adults: Health consequences".)
A BMI of 18.5 to 25 kg/m2 is associated with little or no increased health risks and, for this reason, is desirable for both women and men irrespective of fertility issues. (See "Overweight and obesity in adults: Health consequences".)
Effect on fertility
Female partner
●Elevated body mass index (BMI) – Both overweight (25.0 to 29.9 kg/m2) and obese (≥30 kg/m2) BMIs have been associated with decreased fertility [58].
•Time to pregnancy and pregnancy rates – Obesity in childhood contributes to menstrual cycle abnormalities and infertility [59]. A cross-sectional study in the United States reported that adolescents who self-reported being obese (BMI >30 kg/m2) were more than twice as likely to remain childless than normal-weight adolescents after adjusting for confounding variables such as adult BMI, nongestational amenorrhea, marital status, ethnicity, geographical location, and socioeconomic status [60]. Even in regularly ovulating women, increasing obesity appears to be associated with decreasing spontaneous pregnancy rates and increased time to pregnancy [61-63]. In addition to absolute body weight, weight gain in adulthood may also increase the amount of time needed to conceive, irrespective of baseline weight or menstrual cyclicity. As an example, a prospective cohort study of nearly 2000 women reported that every 5 kg body weight increase (from the patient's baseline weight at age 18) was associated with a 5 percent increase in the mean duration of time needed for attempted conception (95% CI 3-7 percent) [64]. Of note, approximately 90 percent of the women in this study had regular menstrual cycles which suggests that altered ovulation was not the mechanism. Therefore, women who wish to conceive are counseled about the importance of achieving and maintaining a normal weight.
-Ovulatory dysfunction – Most studies in adults report a BMI greater than 27 kg/m2 or a BMI less than 17 kg/m2 is associated with increased ovulatory dysfunction and resultant infertility [65-67].
-Metabolic changes – For women with an elevated BMI, subfertility appears to be related to insulin resistance leading to insulin excess [68]. Hyperinsulinemia may lead to androgen excess by reducing sex-hormone-binding globulin synthesis, thereby increasing free testosterone, and by stimulating ovarian androgen production rates. Excess androgen, in turn, is a major factor leading to altered hypothalamic-pituitary and ovarian physiology and anovulation. Obesity-associated hyperleptinemia may be an additional factor in anovulation, not only through the induction of insulin resistance, but also through direct impairment of ovarian function. Factors other than anovulation also likely play a role in obesity-related subfertility [69]. (See "Diagnosis of polycystic ovary syndrome in adults".)
•Weight loss – Prior observational studies have reported both nonsurgical [70-72] and surgical [73-79] weight loss increased the frequency of ovulation and natural conception. However, weight reduction does not appear to be associated with increased fecundability [80]. A large, multicenter trial of obese (BMI ≥29 kg/m2) and infertile women reported no difference in birth rates of term singletons or overall live birth rates among women who received a six-month structured weight-loss intervention prior to infertility treatment and control women who went directly to infertility treatment [81]. There were also no differences in the obstetric outcomes of gestational diabetes or hypertensive disorders of pregnancy between intervention and control groups. In the trial, women in the intervention group were more likely to conceive spontaneously (26 versus 16 percent) and underwent fewer fertility treatment cycles (679 versus 1067 treatment cycles) compared with the control women. Study limitations include that target weight loss was reached by only 38 percent of women in the intervention group and the intervention discontinuation rate was 22 percent. It is not known if greater weight reduction per person, increased proportion of women reaching target weight loss, or increased patient continuation rates would increase fecundability.
We continue to advise weight loss for infertile women with an elevated BMI because weight reduction aids in spontaneous conception in some studies and reduces the need for fertility treatment, in addition to providing long-term benefits for overall health [70,72]. In a study of 67 women who had an average weight loss of 10 kg over six months, spontaneous ovulatory cycles resumed in nearly 90 percent (60 of 67), with 52 women becoming pregnant and 45 having a live birth. None of the control patients, consisting of study drop-outs, resumed ovulatory cycles or conceived. One lifestyle modification to achieve weight loss includes increased moderate physical activity, such as walking 150 minutes weekly [82,83]. Dietary intake should be decreased by 500 to 1000 cal/day, which will result in a 1 to 2 pound weekly weight loss. Consuming a low-calorie diet of 1000 to 2000 kcal/day should result in a 10 percent decrease in BMI over six months [84]. Maintaining a 10 percent weight loss with lifestyle modification is uncommon and only achieved by 20 percent after one year [85]. Those participating in a lifestyle moderation program may have an improved chance of maintaining weight reduction as compared with those not in a structural program [86]. (See "Obesity in adults: Overview of management".)
●Underweight – The association between low BMI (≤18.5 kg/m2) and infertility is also related to ovulatory dysfunction, although the mechanism differs from that in obese women. Underweight women, particularly those who exercise excessively and/or have low calorie intake, may have hypothalamic amenorrhea. In these women, suppression of pulsatile gonadotropin-releasing hormone (GnRH) secretion from the hypothalamus results in decreased secretion of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) and therefore loss of ovarian cyclicity and estrogen deficiency. Changes in leptin may also be involved. The cohort study above also reported that women who were underweight at age 18 (BMI less than 18.5) had a 25 percent increase in duration of attempted conception compared with women of normal weight. The majority of women in both groups reported regular menses. (See "Functional hypothalamic amenorrhea: Pathophysiology and clinical manifestations" and "Eating disorders: Overview of epidemiology, clinical features, and diagnosis".)
Underweight infertile women may benefit from weight gain, which may improve the frequency of ovulation and therefore the likelihood of pregnancy. As an example, a study of 26 infertile women with a mean BMI of 19.2 kg/m2 employed counseling by a dietitian and clinician-directed advice to increase BMI [87]. These women gained a mean 3.7 kg and 73 percent conceived after these interventions. Limitations of this study include lack of a control group and nonrandomized design.
Male partner — The impact of the male partner's BMI on fertility has not been examined extensively. Some observational and animal data suggest an association between increasing male BMI and lower pregnancy rates [88-90]. There is consistent evidence that obesity affects reproductive hormone levels, but studies have reported conflicting results on the effect of obesity on semen parameters [91-94]. An observational study of nearly 4000 sperm donors in China, with an average of eight repeated semen measures per donor, reported that being underweight (BMI <18.5 kg/m2) was associated with lower sperm concentration, total sperm number, and total motile sperm count while being overweight (BMI 25.0 to 29.9 kg/m2) was associated with lower semen volume, total sperm number, and total motile sperm count [95]. The study controlled for age, ethnicity, education, smoking status, marital status, abstinence period, and season. Only 1 percent (n = 38) of the study population were obese (BMI ≥30 kg/m2), which limited the study's ability to identify statistical significance at this weight level. While weight reduction can correct the hormonal imbalance, the effect of weight loss on semen parameters and pregnancy rate has not been studied.
Effect of obesity on fertility therapy — Some studies report poorer outcomes of infertility treatment in obese women (eg, insufficient follicular development, lower oocyte counts, lower fertilization rates) [96-100], while others report outcomes are comparable to nonobese women, but higher doses of ovulation inducing agents need to be used [101-104]. The risk of unsuccessful IVF increases with increasing BMI and may be related to poor oocyte quality, ovarian function, endometrial quality, or a combination of these factors. In a systematic review and meta-analysis including 33 studies and almost 48,000 IVF/ICSI treatment cycles, women who were overweight or obese (BMI ≥25 kg/m2) had a statistically significant small reduction in clinical pregnancy rate (RR 0.90) and live birth rate (RR 0.84) and a significantly higher miscarriage rate (RR 1.31) than normal weight women (BMI <25 kg/m2) [105].
●Females – Studies have reported poor oocyte quality in obese women, and some, but not all, studies have reported decreased fertilization rates [100,106-110]. A retrospective cohort study noted decreased live birth rates in gestational carriers with a BMI >35 kg/m2 compared with those with a BMI <35 kg/m2 (25 versus 49 percent live birth rate) [111]. A different retrospective study reported both lower fertilization and clinical pregnancy rates for obese versus normal weight women (64 versus 82 percent and 15 versus 33 percent, respectively) [100]. These differences in clinical pregnancy and live birth rates suggest obesity may impair endometrial receptivity. Although obesity is associated with decreased chances of pregnancy in women undergoing IVF with autologous oocytes, a systematic review of IVF outcomes in obese women who received donor oocytes did not observe significant negative effects of obesity on outcome compared with nonobese donor oocyte recipients (clinical pregnancy RR 0.97, 95% CI 0.83-1.16) [112]. This suggests that obesity-mediated subfertility is related, at least in part, to egg quality and perhaps endometrial receptivity. It is also possible that endometrial preparation and monitoring in donor oocyte IVF cycles, which differs from that in fresh autologous cycles, alter some of the adverse effects related to obesity.
However, methodologic problems concerning patient selection, inadequate description of cases, retrospective scientific design, and lack of information on important confounding factors (eg, male partner obesity, smoking habits, fat distribution, or associated pathologies) have prevented clear conclusions or consensus on the effects of obesity on fertility and therapy of subfertility [113].
●Males – Although data are limited, males being overweight and obese has not been associated with altered outcomes following various fertility therapies [114,115]. In one study of nearly 8000 women with a normal BMI (BMI 21 kg/m2) with singleton pregnancies conceived using cryopreserved embryos, investigators reported that the percentage of newborns weighing ≥4000 grams was greater if the male partner was overweight (9.5 percent) or obese (10.0 percent) compared with male partners who were normal weight (7.8 percent) [116].
Spontaneous abortion — Most studies report an increased spontaneous abortion (SAB) rate in obese women undergoing ART [104,105,107,109,117-121]. A meta-analysis of 33 studies reported a slightly higher SAB rate (RR 1.31) in women with a BMI >25 kg/m2 compared with those with a BMI <25 kg/m2 (90 g). An increased risk for pregnancy loss was also noted in those with a BMI >25 kg/m2 following single fresh (OR 2.7, 95% CI 1.5-4.9) or frozen blastocyst transfer [120].
Exercise — Female fertility can be adversely affected by increased intensity and duration of exercise. For this reason, we suggest women with BMI <25 kg/m2 who are attempting to conceive limit vigorous exercise to fewer than five hours per week. Male fertility does not appear to be affected by exercise.
Female partner — The intensity and duration of exercise can affect female fertility, but the specific type of exercise does not appear to be a factor. In some epidemiological studies, vigorous/intense physical activity was associated with ovulatory infertility [122,123], while others have not observed a significant association [124]. Baseline patient characteristics appear to play a role. In a well-designed study of Danish women, vigorous physical activity (running, fast cycling, aerobics, swimming, gymnastics) was associated with a reduction in fecundity; however, the effect was confined to women with a BMI <25 kg/m2; there was a slightly positive effect of all levels of exercise among overweight and obese women [125]. In women undergoing IVF, another study noted that ≥4 hours of strenuous exercise weekly over a period of years was associated with poorer outcomes [126].
The effects of strenuous exercise on fertility could be related to (1) reduced progesterone production during the luteal phase of the menstrual cycle in ovulatory women (ie, luteal phase defect), (2) alterations in GnRH production, LH and FSH secretion, and estradiol production and metabolism, resulting in anovulation, or (3) changes in leptin levels [127-129]. Other factors may include decreased body fat and changes in diet, such as an increase in fiber and a decrease in fat intake, in women who exercise strenuously. (See "Functional hypothalamic amenorrhea: Pathophysiology and clinical manifestations".)
However, from a population perspective, inadequate levels of exercise associated with obesity may be a more common cause of anovulation and subsequent infertility than exercise-associated anovulation [130,131]. (See 'Overweight and obesity' above.)
Male partner — The relationship between fertility and exercise in the male has not been well characterized. One large retrospective study examined the association between regular physical exercise and semen quality in 2261 men whose partners were undergoing IVF [132]. Overall, none of the semen parameters studied was affected by exercise; however, men who bicycled ≥5 hours/week demonstrated lower sperm concentrations and lower numbers of total motile sperm than their non-exercising counterparts; pregnancy rates were not evaluated. Results were not influenced by age, BMI or a history of male infertility.
Alcohol intake — Moderate alcohol consumption <2 drinks/day (1 drink = 10 g of ethanol) probably has no or minimal adverse effects on fertility, but higher levels of alcohol consumption should probably be avoided when attempting pregnancy [1,20,133-135]. Abstinence at conception and during pregnancy is generally recommended because a safe level of prenatal alcohol consumption has not been established. In both men and women, the dose-response relationship between alcohol intake and fertility requires additional study.
Female partner — Most observational studies have reported moderate and heavy female drinkers tend to take longer to achieve a pregnancy and are at higher risk of undergoing an infertility evaluation [133,134,136-138]. Others have not noted an adverse effect of moderate alcohol intake on fertility [139,140] nor a difference in risk of ovulatory dysfunction between women with high versus low alcohol intake [141]. Heavy alcohol intake is typically defined as ≥14 drinks per week, and moderate intake is usually defined as 3 to 13 drinks per week, but these definitions are arbitrary and vary in different studies. However, alcohol consumption can impact the developing fetus. (See "Alcohol intake and pregnancy".)
Moderate alcohol use may affect success rates of women undergoing IVF, but the supporting data are mixed. A retrospective study on alcohol consumption reported that women who drank at least four drinks per week were at 16 percent less odds of a live birth after IVF compared with women who had fewer drinks (OR 0.84, CI 0.71-0.99) [142]. By contrast, a prospective study of 300 women undergoing IVF failed to find an association between alcohol conception and live birth. The authors divided their subjects corresponding to <0.5 glass of alcohol/day, 0.5 to 1 glass/day, 1 to 2 glasses/day, and >2 glasses per day. No difference in live births was observed [143]. A Danish cohort study involving over 1700 women and their partners who underwent intrauterine insemination, IVF, or ICSI treatment failed to demonstrate an effect of alcohol consumption on any of the three treatment modalities for 1 to 2, 3 to 7, and >7 drinks per week. For the IVF/ICSI groups, the adjusted relative risk of achieving live birth was 1.00 (95% CI 0.83-1.21), 0.95 (95% CI 0.75-1.20), and 0.89 (95% CI 0.53-1.51) for 1 to 2, 3 to 7, and >7 drinks per week, respectively, compared with a nondrinking cohort [144].
Male partner — Heavy alcohol use by the male partner is related to abnormalities in gonadal function, including reduced testosterone production, impotence, and decreased spermatogenesis [145-147]. In the IVF study cited above [142], in couples in which both partners consumed at least four drinks per week, the odds of a live birth were diminished by 21 percent compared with couples in which both partners drank less than four or more drinks per week. For patients with a live birth, a meta-analysis of 55 studies reported paternal alcohol use prior to conception was associated with an increased risk of total congenital heart defects in the offspring (OR 1.44, 95% CI 1.19-1.74) [148].
Diet — In healthy couples, there is no strong evidence that dietary variations such as vegetarian diets, low-fat diets, and vitamin or antioxidant-enriched diets improve fertility [20,149]. However, undiagnosed/untreated celiac disease may cause female or male subfertility, which resolves by adopting a gluten-free diet. (See "Epidemiology, pathogenesis, and clinical manifestations of celiac disease in adults".)
Female partner — Data on the relationship between diet and fertility in women are from observational studies. One of the largest of these studies was a prospective cohort study of over 18,000 married, premenopausal women without a history of infertility who attempted pregnancy or became pregnant [124,150-154]. Based on their own data and that from other studies, the authors considered the following dietary habits components of a "fertility diet": higher monounsaturated to trans-fat ratio, high percentage of protein from vegetable rather than animal sources, low glycemic index carbohydrates, high fat dairy foods, and use of iron and multivitamin supplements. Healthy women whose diet reflected this composition had a significantly reduced risk of ovulatory disorder infertility. They hypothesized that this diet was favorable to glucose homeostasis and insulin sensitivity, factors that play a role in ovulatory function. The results were based on dietary recall, and thus were subject to recall bias. Other smaller observational studies have supported the beneficial effects of a Mediterranean diet, reduced trans-fat intake, and increased omega-3 fatty acid intake on achieving natural or assisted conception [155-158]. There is no harm to such diets, but no strong data at this time to recommend dietary changes solely for enhancement of fertility.
Male partner — Observational studies in men have reported improved semen parameters among men with healthy dietary habits; pregnancy rates were not evaluated [159-161].
Caffeine — Female fertility does not appear to be affected by caffeine intake less than 200 mg per day, even for women undergoing IVF therapy [143,162]. A cohort study of over 1700 couples undergoing fertility treatment reported a higher chance of a live birth among women consuming 1 to 5 cups of coffee per day compared with a relevant non-coffee drinking cohort (adjusted relative risk 1.53, 95% CI 1.06-2.21) [163]. Therefore, women contemplating pregnancy probably can have one or two 6 to 8 ounce cups of coffee per day without negatively impacting their ability to conceive (table 1). The impact of caffeine consumption on fertility and reproductive outcomes is presented in detail elsewhere. (See "Caffeine: Effects on reproductive outcomes in females".)
There is no strong evidence to support limiting caffeine intake in the male partner.
Stress — Many observational studies have suggested that stress is associated with infertility and, in turn, the diagnosis and treatment of infertility clearly can be stressful. No clinical trial has demonstrated definitively that reducing stress prior to infertility treatment improves pregnancy rates. (See "Psychological stress and infertility".)
●Impact of stress on assisted reproductive outcomes – In a 2011 meta-analysis that pooled 31 prospective trials examining the association between stress, distress in female patients, and assisted reproductive technology (ART) outcomes, small but statistically significant negative correlations were observed between ART outcomes and stress and anxiety [164]. Importantly, however, the association with anxiety disappeared when live birth rates were examined, and too few trials using stress were included to allow statistical analysis.
●Impact of stress reduction – A 2021 meta-analysis of 15 trials evaluating the impact of psychosocial interventions for individuals undergoing assisted reproductive technology reported a small but significant increase in live birth rate with psychosocial interventions, particularly long-term and mind-body interventions (risk ratio 1.21, 95% CI 1.04-1.43 and risk ratio 1.25, 95% CI 1.00-1.55, respectively) [165]
Environmental factors — Environmental pollutants and toxicants, such as dry cleaning solvents, heavy metals, pesticides, and possibly bisphenol A (BPA) can have adverse effects on fertility and pregnancy. (See "Overview of occupational and environmental risks to reproduction in females".)
A review of studies on sauna bathing concluded that this activity does not influence fertility in women or men [166]. Although hormonal changes occur during sauna bathing, the changes are transient.
Recreational drug use — There are minimal data on the effects of recreational drug use on fertility [167]. A study of self-reported marijuana use by individuals undergoing fertility treatment reported a higher risk of pregnancy loss in marijuana smokers compared with past or never-users (n = 308, 379 cycles, adjusted probability 54 versus 26 percent) [168]. Unexpectedly, a higher pregnancy rate was reported for couples undergoing IVF when the male partner smoked marijuana while the female partner did not. These drugs should be avoided because of their general health risks.
●(See "Substance use during pregnancy: Screening and prenatal care".)
●(See "Substance use during pregnancy: Overview of selected drugs".)
Sexual behavior — Untreated chlamydial and gonococcal infection may result in pelvic inflammatory disease, which can lead to female infertility. In the years prior to attempting pregnancy, individuals should adopt sexual behaviors, such as condom use, that reduce the risk of acquiring these and other sexually transmitted infections. (See "Prevention of sexually transmitted infections".)
LIFESTYLE EFFECTS ON ESTABLISHED PREGNANCY — Cigarette smoking, obesity, alcohol and caffeine consumption, and recreational drug use can have a significant adverse impact on pregnancy and fetal outcomes. The combined impact of these exposures on both fertility and pregnancy outcome emphasizes the importance of lifestyle interventions for the couple planning a pregnancy. (See "The preconception office visit".)
●(See "Cigarette and tobacco products in pregnancy: Impact on pregnancy and the neonate".)
●(See "Obesity in pregnancy: Complications and maternal management".)
●(See "Alcohol intake and pregnancy" and "Infants with prenatal substance use exposure", section on 'Alcohol: Fetal alcohol spectrum disorder'.)
●(See "Substance use during pregnancy: Screening and prenatal care".)
●(See "Caffeine: Effects on reproductive outcomes in females".)
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Female infertility".)
SUMMARY AND RECOMMENDATIONS — Lifestyle factors can affect the duration of time before achieving pregnancy and modifying these factors may enhance fertility. The recommendations below are based upon data from observational studies; no randomized trials have been performed.
●Couples should be informed that delayed childbearing, especially after age 30 years, can decrease the probability of successful conception, and they should take this into account in family and career planning. (See 'How does age affect fertility?' above.)
●We suggest sexual intercourse two to three times per week from soon after cessation of menses through the day of ovulation to ensure that intercourse falls within the most fertile period (up to two days before ovulation) and semen quality is optimal (Grade 2C). (See 'When is the fertile period of the cycle?' above.)
●We recommend smoking cessation for couples who smoke based on the overall health benefits of smoking cessation (Grade 1A). Use of tobacco by the female partner, and possibly the male partner, appears to be associated with subfertility. For couples planning pregnancy, observational studies suggest fertility is enhanced when use of tobacco products is terminated. (See 'Tobacco use' above.)
●A body mass index (BMI) greater than 27 kg/m2 or less than 17 kg/m2 is associated with an increased risk of anovulatory infertility. The former is often related to polycystic ovary syndrome and the latter is often related to amenorrhea caused by excessive exercise or poor caloric intake (eg, eating disorders). We suggest couples try to achieve a BMI of 18.5 to 25 kg/m2 (Grade 2C). Women in this weight range are less likely to have ovulatory dysfunction than women at either extreme of BMI. This range is associated with little or no increased health risks and, for this reason, is desirable for both women and men. There is little information on the relationship between male fertility and BMI. (See 'Overweight and obesity' above.)
●Moderate and heavy female drinkers tend to take longer to achieve a pregnancy and are at higher risk of undergoing an infertility evaluation. We suggest that women who are attempting to conceive avoid all alcohol, given a safe level of prenatal alcohol consumption with respect to the fetus has not been determined (Grade 2C). Moderate alcohol intake by the male partner does not appear to be associated with decreased fertility. (See 'Alcohol intake' above.)
●It is unclear whether high caffeine consumption affects female fertility; it does not appear to affect male fertility. We suggest women contemplating pregnancy limit caffeine intake to no more than one or two cups of coffee per day (total of 200 mg caffeine) (Grade 2C). (See 'Caffeine' above.)
1 : Negative lifestyle is associated with a significant reduction in fecundity.
2 : Preconception lifestyle advice for people with subfertility.
3 : Predictors of pregnancy and live birth after insemination in couples with unexplained or male-factor infertility.
4 : The FAST study: Fertility ASsessment and advice Targeting lifestyle choices and behaviours: a pilot study.
5 : The International Glossary on Infertility and Fertility Care, 2017.
6 : Studying time to pregnancy by use of a retrospective design.
7 : Time to pregnancy: results of the German prospective study and impact on the management of infertility.
8 : Estimates of human fertility and pregnancy loss.
9 : Definition and prevalence of subfertility and infertility.
10 : Day-specific probabilities of clinical pregnancy based on two studies with imperfect measures of ovulation.
11 : The length of the fertile window is associated with the chance of spontaneously conceiving an ongoing pregnancy in subfertile couples.
12 : Timing of sexual intercourse in relation to ovulation. Effects on the probability of conception, survival of the pregnancy, and sex of the baby.
13 : New estimates of the effectiveness of the Yuzpe regimen of emergency contraception.
14 : Models relating the timing of intercourse to the probability of conception and the sex of the baby.
15 : Probability of conception on different days of the menstrual cycle: an ongoing exercise.
16 : Conception probabilities at different days of menstrual cycle in Chinese women.
17 : Optimizing natural fertility: a committee opinion.
18 : Findings from a mobile application-based cohort are consistent with established knowledge of the menstrual cycle, fertile window, and conception.
19 : Home ovulation tests and stress in women trying to conceive: a randomized controlled trial.
20 : Optimizing natural fertility: a committee opinion.
21 : Timed intercourse for couples trying to conceive.
22 : Duration of sexual abstinence: epididymal and accessory sex gland secretions and their relationship to sperm motility.
23 : Relationship between the duration of sexual abstinence and semen quality: analysis of 9,489 semen samples.
24 : Effect of time interval between ejaculations on semen parameters.
25 : Effects of sexual intercourse patterns in time to pregnancy studies.
26 : Effect of ejaculatory abstinence period on the pregnancy rate after intrauterine insemination.
27 : Effect of vaginal lubricants on sperm motility and chromatin integrity: a prospective comparative study.
28 : Evaluation of Astroglide, a new vaginal lubricant: effects of length of exposure and concentration on sperm motility.
29 : The effects of coital lubricants on sperm motility in vitro.
30 : The effect of vaginal lubricants on sperm motility in vitro.
31 : Vaginal lubricants for the infertile couple: effect on sperm activity.
32 : In vitro effects of coital lubricants and synthetic and natural oils on sperm motility.
33 : Effect of vaginal lubricants on natural fertility.
34 : Increased infertility with age in men and women.
35 : Changes with age in the level and duration of fertility in the menstrual cycle.
36 : The relationship of tubal infertility to barrier method and oral contraceptive use.
37 : The association between smoking and female infertility as influenced by cause of the infertility.
38 : Periconception window: advising the pregnancy-planning couple.
39 : Smoking and infertility: a committee opinion.
40 : Effects of age, cigarette smoking, and other factors on fertility: findings in a large prospective study.
41 : Randomized trial of a "stage-of-change" oriented smoking cessation intervention in infertile and pregnant women.
42 : Does cigarette smoking impair natural or assisted fecundity?
43 : Effects of cigarette smoking, caffeine consumption, and alcohol intake on fecundability.
44 : Smoking and female infertility: a systematic review and meta-analysis.
45 : Smoking reduces fecundity: a European multicenter study on infertility and subfecundity. The European Study Group on Infertility and Subfecundity.
46 : [Tobacco and ectopic pregnancy. Arguments in favor of a causal relation].
47 : Determinants of basal follicle-stimulating hormone levels in premenopausal women.
48 : Cigarette smoking and the age at menopause.
49 : Smoking induces oxidative stress inside the Graafian follicle.
50 : Effect of cigarette smoking on DNA damage of human cumulus cells analyzed by comet assay.
51 : Environment, lifestyle and infertility--an inter-generational issue.
52 : Reduced fecundability in women with prenatal exposure to cigarette smoking.
53 : Does smoking during pregnancy affect sons' sperm counts?
54 : Smoking and male reproduction: a review.
55 : Male smokers have a decreased success rate for in vitro fertilization and intracytoplasmic sperm injection.
56 : [What are the epidemiological data on maternal and paternal smoking?].
57 : Risk of major congenital malformations in relation to maternal overweight and obesity severity: cohort study of 1.2 million singletons.
58 : Association of maternal pre-pregnancy low or increased body mass index with adverse pregnancy outcomes.
59 : Women's reproductive health: the role of body mass index in early and adult life.
60 : Association of adolescent obesity and lifetime nulliparity--the Study of Women's Health Across the Nation (SWAN).
61 : Obesity affects spontaneous pregnancy chances in subfertile, ovulatory women.
62 : Obesity and time to pregnancy.
63 : Subfecundity in overweight and obese couples.
64 : Association of Fecundity With Changes in Adult Female Weight.
65 : Body mass index and ovulatory infertility.
66 : Adolescent body mass index and infertility caused by ovulatory disorder.
67 : Body mass index, physical activity and fecundability in a North American preconception cohort study.
68 : Metabolic effects of obesity on reproduction.
69 : The effect of increasing obesity on the response to and outcome of assisted reproductive technology: a national study.
70 : Weight loss results in significant improvement in pregnancy and ovulation rates in anovulatory obese women.
71 : Improving reproductive performance in overweight/obese women with effective weight management.
72 : Weight loss in obese infertile women results in improvement in reproductive outcome for all forms of fertility treatment.
73 : Pregnancy after Lap-Band surgery: management of the band to achieve healthy weight outcomes.
74 : Obesity and reproduction: impact and interventions.
75 : Outcome of pregnancies after biliopancreatic diversion.
76 : Pregnancy after adjustable gastric banding.
77 : Outcome after laparoscopic adjustable gastric banding - 8 years experience.
78 : Effective treatment of polycystic ovarian syndrome with Roux-en-Y gastric bypass.
79 : The impact of bariatric surgery on menstrual patterns.
80 : Pharmacological and non-pharmacological strategies for obese women with subfertility.
81 : Randomized Trial of a Lifestyle Program in Obese Infertile Women.
82 : Standards of medical care in diabetes--2013.
83 : Update on treatment strategies for obesity.
84 : Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults--The Evidence Report. National Institutes of Health.
85 : Successful weight loss maintenance.
86 : Behavioral treatment of obesity.
87 : Reproductive failure in women who practice weight control.
88 : Reduced fertility among overweight and obese men.
89 : Men's body mass index and infertility.
90 : Paternal diet-induced obesity impairs embryo development and implantation in the mouse.
91 : Semen parameters and hormonal profile in obese fertile and infertile males.
92 : Healthy overweight male partners of subfertile couples should not worry about their semen quality.
93 : Body mass index and central adiposity are associated with sperm quality in men of subfertile couples.
94 : High body mass index has a deleterious effect on semen parameters except morphology: results from a large cohort study.
95 : Association between BMI and semen quality: an observational study of 3966 sperm donors.
96 : Body mass and probability of pregnancy during assisted reproduction treatment: retrospective study.
97 : Anthropometric indicators and response to gonadotrophin for ovulation induction.
98 : The influence of female and male body mass index on live births after assisted reproductive technology treatment: a nationwide register-based cohort study.
99 : Female obesity is negatively associated with live birth rate following IVF: a systematic review and meta-analysis.
100 : The Role of Overweight and Obesity in In Vitro Fertilization Outcomes of Poor Ovarian Responders.
101 : Effect of overweight and obesity on assisted reproductive technology--a systematic review.
102 : The influence of body weight on response to ovulation induction with gonadotrophins in 335 women with World Health Organization group II anovulatory infertility.
103 : The effect of obesity on the outcome of infertility management in women with polycystic ovary syndrome.
104 : Women, weight, and fertility: the effect of body mass index on the outcome of superovulation/intrauterine insemination cycles.
105 : Effect of body mass index on IVF treatment outcome: an updated systematic review and meta-analysis.
106 : Oocyte morphological abnormalities in overweight women undergoing in vitro fertilization cycles.
107 : Overweight and obesity negatively affect the outcomes of ovarian stimulation and in vitro fertilisation: a cohort study of 2628 Chinese women.
108 : The influence of body mass index on in vitro fertilization outcome.
109 : Impact of overweight and underweight on assisted reproduction treatment.
110 : Effect of increased body mass index on oocyte and embryo quality in IVF patients.
111 : Surrogate obesity negatively impacts pregnancy rates in third-party reproduction.
112 : IVF outcomes in obese donor oocyte recipients: a systematic review and meta-analysis.
113 : Obesity and poor reproductive outcome: female and male body weight matter.
114 : The role of paternal obesity on the success of intracytoplasmic sperm injection cycle a tertiary IVF center in Turkey.
115 : Impact of male partner characteristics and semen parameters on in vitro fertilization and obstetric outcomes in a frozen oocyte donor model.
116 : Effect of paternal body mass index on neonatal outcomes of singletons after frozen-thawed embryo transfer cycles: analysis of 7,908 singleton newborns.
117 : Patient predictors for outcome of gonadotrophin ovulation induction in women with normogonadotrophic anovulatory infertility: a meta-analysis.
118 : The effect of body mass index on the outcomes of first assisted reproductive technology cycles.
119 : Fat and female fecundity: prospective study of effect of body fat distribution on conception rates.
120 : Influence of BMI on risk of miscarriage after single blastocyst transfer.
121 : Obesity increases the risk of spontaneous abortion during infertility treatment.
122 : Exercise as a risk factor for infertility with ovulatory dysfunction.
123 : Physical activity and fertility in women: the North-Trøndelag Health Study.
124 : Diet and lifestyle in the prevention of ovulatory disorder infertility.
125 : A prospective cohort study of physical activity and time to pregnancy.
126 : Effects of lifetime exercise on the outcome of in vitro fertilization.
127 : Induction of menstrual disorders by strenuous exercise in untrained women.
128 : Salivary steroids and natural variation in human ovarian function.
129 : Estrogen and exercise may be related to body fat distribution and leptin in young women.
130 : Obesity in Britain: gluttony or sloth?
131 : Physical activity, body mass index, and ovulatory disorder infertility.
132 : Physical activity and semen quality among men attending an infertility clinic.
133 : Does moderate alcohol consumption affect fertility? Follow up study among couples planning first pregnancy.
134 : Effects of alcohol consumption on female fertility during an 18-year period.
135 : Alcohol and caffeine consumption and decreased fertility.
136 : Does moderate alcohol intake reduce fecundability? A European multicenter study on infertility and subfecundity. European Study Group on Infertility and Subfecundity.
137 : Moderate alcohol consumption and waiting time to pregnancy.
138 : Fertility in Norwegian women: results from a population-based health survey.
139 : Alcohol use as predictor for infertility in a representative population of Danish women.
140 : Alcohol consumption is not related to fertility in Italian women.
141 : Caffeinated and alcoholic beverage intake in relation to ovulatory disorder infertility.
142 : Effect of alcohol consumption on in vitro fertilization.
143 : The association between pre-treatment maternal alcohol and caffeine intake and outcomes of assisted reproduction in a prospectively followed cohort.
144 : Low-to-moderate alcohol consumption and success in fertility treatment: a Danish cohort study.
145 : A comparative study of cytological and physiological parameters of semen obtained from alcoholics and non-alcoholics.
146 : Effect of chronic alcoholism on semen--studies on lipid profiles.
147 : Alcohol's effects on male reproduction.
148 : Parental alcohol consumption and the risk of congenital heart diseases in offspring: An updated systematic review and meta-analysis.
149 : Antioxidants for female subfertility.
150 : Dietary fatty acid intakes and the risk of ovulatory infertility.
151 : Iron intake and risk of ovulatory infertility.
152 : A prospective study of dairy foods intake and anovulatory infertility.
153 : Protein intake and ovulatory infertility.
154 : Use of multivitamins, intake of B vitamins, and risk of ovulatory infertility.
155 : Dietary patterns and difficulty conceiving: a nested case-control study.
156 : The preconception Mediterranean dietary pattern in couples undergoing in vitro fertilization/intracytoplasmic sperm injection treatment increases the chance of pregnancy.
157 : Dietary Fat Intake and Fecundability in 2 Preconception Cohort Studies.
158 : Intake of protein-rich foods in relation to outcomes of infertility treatment with assisted reproductive technologies.
159 : Food intake and its relationship with semen quality: a case-control study.
160 : The role of lifestyle changing to improve the semen quality in patients with varicocele.
161 : Dairy intake and semen quality among men attending a fertility clinic.
162 : Association between preconception maternal beverage intake and in vitro fertilization outcomes.
163 : Impact of female daily coffee consumption on successful fertility treatment: a Danish cohort study.
164 : Stress, distress and outcome of assisted reproductive technology (ART): a meta-analysis.
165 : The association between psychosocial interventions and fertility treatment outcome: A systematic review and meta-analysis.
166 : Benefits and risks of sauna bathing.
167 : Recreational drug use and the risk of primary infertility.
168 : Marijuana smoking and outcomes of infertility treatment with assisted reproductive technologies.
