INTRODUCTION — Uterine fibroids (leiomyomas) are benign smooth muscle tumors of the uterus. The potential effects of fibroids on pregnancy and the potential effects of pregnancy on fibroids are a frequent clinical concern since these tumors are common in women of reproductive age. Most pregnant women with fibroids do not have any complications during pregnancy related to the fibroids. Pain is the most common problem, and there may be a slightly increased risk of obstetric complications, such as miscarriage, preterm labor and delivery, fetal malpresentation, and placental abruption.

This topic will review issues specifically relating to pregnant women with uterine fibroids. Fibroids in nonpregnant women, including fertility issues, are discussed separately. (See "Uterine fibroids (leiomyomas): Epidemiology, clinical features, diagnosis, and natural history" and "Uterine fibroids (leiomyomas): Treatment overview".)

LIMITATIONS OF AVAILABLE EVIDENCE — Several factors make it difficult to assess the impact of fibroids on pregnancy outcome and to identify specific fibroid characteristics that are important. For example, interpretation of available evidence is limited by the heterogeneity of the study populations, which differ in method of ascertainment (eg, prospective versus retrospective study design), gestational age at diagnosis, and fibroid characteristics (number, size, location [fundus, lower uterine segment], type [submucosal, intramural, subserosal; pedunculated or sessile]). Small numbers of adverse events, ascertainment bias in selecting study participants, and inadequate adjustment of confounders also play a role. In addition, small fibroids (<4 to 5 cm) may not be detected consistently because they can be difficult to distinguish from physiologically thickened myometrium. Lastly, the mechanisms whereby fibroids may cause adverse obstetric outcomes are not clearly understood.

PREVALENCE — The reported prevalence of uterine fibroids in pregnancy varies between 1.6 and 10.7 percent, depending upon the trimester of assessment (first versus second) and the size threshold for reporting presence of a fibroid (eg, range ≥0.5 to >3 cm) [1-5]. (See "Uterine fibroids (leiomyomas): Epidemiology, clinical features, diagnosis, and natural history", section on 'Prevalence'.)

The prevalence of fibroids increases with maternal age and is higher in Black women than in White or Hispanic women [4]. Increasing parity and prolonged duration of breastfeeding are associated with a small, but statistically significant, reduction in prevalence [6].

CHANGE IN SIZE DURING PREGNANCY AND POSTPARTUM — Change in size of fibroids may be affected by change in estrogen and progesterone levels, uterine blood flow, and, possibly, human chorionic gonadotropin levels.

●Antepartum – The body of evidence suggests that fibroid size remains stable (<10 percent change) across gestation in 50 to 60 percent of cases, increases in 22 to 32 percent, and decreases in 8 to 27 percent [7-9].

Larger fibroids (>5 cm in diameter) are more likely to grow, whereas smaller fibroids are more likely to remain stable in size [3]. The mean increase in fibroid volume during pregnancy is 12 percent, and very few fibroids increase by more than 25 percent [8,9]. The pattern of fibroid growth during pregnancy is probably not linear [7-13]. For those fibroids that increase in size, most of the growth occurs in the first trimester, with little if any further increase in size during the second and third trimesters [7-9,14].

●Postpartum – Almost 90 percent of women with fibroids detected in the first trimester will have regression in total fibroid volume when re-evaluated three to six months postpartum, but 10 percent will have an increase in volume [15]. Regression may be less in women who use progestin-only contraception.

SYMPTOMS — Uterine fibroids are usually asymptomatic during pregnancy. In symptomatic women, symptoms include pain, pelvic pressure, and/or vaginal bleeding.

Pain is the most common symptom (11 percent of women with fibroids were admitted to the hospital for pain in one study [16]). The frequency of pain increases with increasing size and is especially high in women with large fibroids (23 percent of women with fibroids 7 to 10 cm in diameter were admitted for pain in the same study [16]) [2,16,17]. Most patients have only localized pain without other signs and symptoms, although mild leukocytosis, fever, and nausea and vomiting can occur [18,19]. Fibroid pain typically presents in the late first or early second trimester, which corresponds to the period of greatest fibroid growth and, in turn, propensity to degeneration. Pain also may result from partial obstruction of the vessels supplying the fibroid as the uterus grows and changes its orientation to the fibroid [20] or from torsion. (See 'Degeneration and torsion' below.)

Symptoms resulting from ectopic hormone production (eg, erythropoietin [21], parathyroid-related protein [22,23], prolactin) are rare.

COMPLICATIONS — Most pregnant women with fibroids do not have any complications during pregnancy related to the fibroids [24]. When complications occur, painful degeneration is the most common complication. There also appears to be a slightly increased risk of complications such as miscarriage, preterm labor and delivery, fetal malpresentation, and placental abruption, but all studies do not show an increased risk of adverse events. The following list of pregnancy complications begins with those most strongly associated with fibroids and ends with those least associated with fibroids. However, high-quality data on the relationship between fibroids and pregnancy outcome are very limited. (See 'Limitations of available evidence' above.)

Degeneration and torsion — As discussed above (see 'Symptoms' above), pain is one of the most common symptoms of fibroids in pregnant women and is typically due to fibroid degeneration or, rarely, torsion. Rapid growth of fibroids can result in a relative decrease in perfusion, leading to ischemia and necrosis (red degeneration) and release of prostaglandins [25]. Pedunculated fibroids are at risk of torsion and necrosis, but this is much less common than degeneration.

The diagnosis of degeneration and torsion is reviewed separately. (See "Uterine fibroids (leiomyomas): Epidemiology, clinical features, diagnosis, and natural history", section on 'Fibroid degeneration or torsion'.)

Miscarriage — In some patients, submucosal fibroids appear to adversely affect implantation, placentation, and ongoing pregnancy. The effects of intramural fibroids are more controversial, while fibroids that are primarily subserosal or pedunculated are unlikely to cause adverse outcomes. The risk of pregnancy loss may be higher when there are multiple fibroids [26].

The mechanisms by which fibroids may cause pregnancy loss are not known; the following hypotheses have been proposed:

●The fibroid may interfere with placentation and development of normal uteroplacental circulation [27,28]. As an example, a large submucosal fibroid projecting into the uterine cavity may compress the decidualized endometrium, leading to decidual atrophy or distortion of the vascular architecture and blood flow supplying and draining the decidua at that site.

●Rapid fibroid growth with or without degeneration may lead to increased uterine contractility or altered production of catalytic enzymes by the placenta [28,29], both of which may disrupt placentation, leading to spontaneous abortion.

When fibroid location was not considered, a meta-analysis of nine cohort studies found no association between fibroid presence and miscarriage [30].

These issues are discussed in more detail separately. (See "Causes of female infertility", section on 'Uterine fibroids (leiomyomata)'.)

Preterm labor and birth — There appears to be an increase in the baseline risk of preterm labor (unadjusted odds ratio [OR] 1.9, 95% CI 1.5-2.3 [31]) and preterm birth (unadjusted OR 1.5, 95% CI 1.3-1.7 [31]) in pregnancies with uterine fibroids [5,31-34]. Characteristics reported to increase this risk include multiple fibroids, placentation adjacent to or overlying the fibroid [7,16,35], and size greater than 5 cm [36]. As with other complications, this association is not consistent across the literature [2,37-39]. We do not consider fibroids an indication to monitor cervical length for shortening with ultrasound during pregnancy.

Various theories have been proposed to explain the biologic basis of preterm labor in the setting of uterine fibroids. It is possible that fibroid uteri are less distensible than nonfibroid uteri so that contractions occur when the uterus distends beyond a certain point [17,27]. Decreased oxytocinase activity in the gravid fibroid uterus has been noted, which may result in a localized increase in oxytocin levels, thereby predisposing to preterm contractions [29]. (See "Spontaneous preterm birth: Pathogenesis", section on '#4 Pathologic uterine distention' and "Physiology of parturition at term".)

Antepartum bleeding and placental abruption — Numerous studies have reported that antepartum bleeding is more common in pregnancies with fibroids [2,35,40,41], although other studies have not confirmed this association [7,31,37]. The location of the fibroid in relation to the placenta appears to be an important determinant and implies that bleeding is related to abruption. Pooled cumulative data suggest the risk of abruption is increased threefold in women with fibroids; however, the absolute risk remains low since abruption occurs in only 2 to 10 per 1000 births in the overall obstetric population (unadjusted OR 3.2, 95% CI 2.6-4.0) [31].

Submucosal and retroplacental fibroids and fibroids with volumes >200 mL (corresponding to 7 to 8 cm diameter) are associated with the highest risk of abruption [2,17,35,42]. As an example, in a retrospective analysis of over 6700 consecutive pregnant patients, 8/14 patients (57 percent) with retroplacental fibroids developed placental abruption with the deaths of four fetuses, while only two abruptions occurred among the 79 patients (2.5 percent) whose fibroids were not retroplacental, and neither of these resulted in fetal death [17].

A hypothesis for the increased risk of abruption in women with fibroids is that the fibroid causes abnormal perfusion of the placental site [17]. When Xenon-133 was used to measure regional blood flow in the uteri of 11 nonpregnant patients undergoing laparotomy, blood flow was significantly reduced in the myometrium adjacent to fibroids [43]. The authors suggested that the decidua overlying a fibroid may have reduced blood flow, leading to placental ischemia and decidual necrosis, making the area more susceptible to antepartum bleeding and abruption. (See "Placental abruption: Pathophysiology, clinical features, diagnosis, and consequences" and "Placental abruption: Management and long-term prognosis".)

Malpresentation — Müllerian anomalies are associated with an increased risk of malpresentation, presumably because they distort the shape of the uterine cavity [44,45]. In a population-based cohort of over 72,000 consecutive women with singleton pregnancies in Washington state who underwent routine second-trimester fetal anatomic survey at a single university hospital, breech presentation at delivery occurred in 5.3 percent of women with a fibroid uterus compared with 3.1 percent of those without fibroids (adjusted OR 1.5, 95% CI 1.3-1.9) [5].

Large submucosal fibroids that distort the uterine cavity have been consistently associated with high risk of fetal malpresentation (unadjusted OR 2.9, 95% CI 2.6-3.2) [31]. Other characteristics associated with a particularly high risk of malpresentation include multiple fibroids, a fibroid located behind the placenta or in the lower uterine segment, or a large fibroid (eg, over 10 cm) [1,7,17,46].

Dysfunctional labor — Theoretically, fibroids in the myometrium may decrease the force of uterine contractions or disrupt the coordinated spread of the contractile wave, thereby leading to dysfunctional labor and cesarean delivery [39,47]. Several studies have reported an increased incidence of dysfunctional labor in pregnancies complicated by fibroids [39,41,48]; not all investigators have been able to confirm this association [1,37]. Higher rates of tachysystole (defined as >5 contractions in 10 minutes) have also been reported [49].

Cesarean delivery — Studies have consistently reported that uterine fibroids are associated with an increased risk of cesarean delivery (unadjusted OR 3.7, 95% CI 3.5-3.9 [31]), especially when the fibroids are located in the lower uterine segment [1,7,17,18,39,41,48,50-52]. The proposed increase in cesarean delivery rate is likely due to multiple factors, such as an increased risk of malpresentation (see 'Malpresentation' above), dysfunctional labor (see 'Dysfunctional labor' above), obstruction of the birth canal, and fetal heart rate abnormalities related to placental abruption (see 'Antepartum bleeding and placental abruption' above). However, most of these studies were biased in their selection of cases, so a causal association is unproven.

Postpartum hemorrhage — Several studies have reported an increased risk of postpartum hemorrhage in pregnancies complicated by fibroids (unadjusted OR 1.8, 95% CI 1.4-2.2 [31]) [1,42,48], especially if the fibroids are >3 cm and located behind the placenta [25,40,46] or the delivery is by cesarean [48]. However, numerous other studies have found no association between fibroids and postpartum hemorrhage [7,37,39].

Pathophysiologically, fibroids could predispose to postpartum hemorrhage by decreasing both the force and coordination of uterine contractions, thereby leading to uterine atony [47]. This hypothesis is supported by a large retrospective study in which the rate of postpartum hemorrhage was higher in women with intramural fibroids (8.6 percent) than in those with submucosal and subserosal fibroids (4.7 and 5.6 percent, respectively) [53]. By comparison, the baseline incidence of postpartum hemorrhage in the general obstetric population is 1 to 3 percent of deliveries.

Fetal deformities — Spatial restrictions from uterine fibroids can cause fetal deformations, but this is extremely rare. Case reports have described fetal anomalies including limb reduction defects, congenital torticollis, and head deformities in pregnancies with large submucosal fibroids [54-56].

Preterm prelabor rupture of membranes — Pooled cumulative data suggest that fibroids do not increase the risk of preterm prelabor rupture of membranes and may even slightly decrease the risk [31]. However, individual studies have reported conflicting findings [1,2,5,37-41,57]. The location of the fibroid in relation to the placenta may be an important determinant: the greatest risk of preterm prelabor rupture of membranes appears to be when the fibroid is in direct contact with the placenta [40].

Placenta previa — Most studies that account for maternal age and prior uterine surgery failed to show any association between fibroids and placenta previa [7,38,39,41,50], although two large series reported an increased rate (1.4 versus 0.5 percent in controls [5], 3.8 versus 2.0 percent in controls [1]). The latter series adjusted for prior cesarean delivery and myomectomy.

Fetal growth restriction — Fibroids have minimal, if any, effect on fetal growth (unadjusted OR 1.4, 95% CI 1.1-1.7 [31]) [2,7,17,37-39,50]. It is possible, however, that large fibroids (greater than 200 mL) may be associated with delivery of small-for-gestational age infants (<10^th percentile for gestational age) [9].

Other complications — A number of other pregnancy complications have been reported in women with fibroids, including disseminated intravascular coagulation, spontaneous hemoperitoneum, uterine incarceration, urinary tract obstruction with urinary retention or acute renal failure, deep vein thrombosis, and puerperal uterine inversion [46,58-61]. (See "Incarcerated gravid uterus" and "Puerperal uterine inversion".)

Pyomyoma (suppurative leiomyoma) is rare [62-66]. Clinical findings may include fever, leukocytosis, tachycardia, pelvic pain, and characteristic features on imaging studies (heterogeneous mass that may contain gas).

Fetal demise — Rates of fetal demise are not increased in pregnancies complicated by uterine fibroids [41,50].

Preeclampsia — The majority of studies do not support an association between fibroids and preeclampsia [37,38,41], although one study noted that women with multiple fibroids were significantly more likely to develop preeclampsia than those with a single fibroid (45 versus 13 percent) [37]. The authors suggested that the increased risk was due to disruption of trophoblast invasion by the multiple fibroids leading to inadequate uteroplacental vascular remodeling leading to the development of preeclampsia.

MANAGEMENT ISSUES

Indications for preconception myomectomy — Decisions regarding preconception myomectomy are made on a case-by-case basis and depend on several factors, including the age of the patient, her past reproductive history, the severity of her symptoms, and the size and location of the fibroids. These issues are reviewed elsewhere:

●(See "Uterine fibroids (leiomyomas): Treatment overview", section on 'Patients desiring fertility'.)

●(See "Recurrent pregnancy loss: Definition and etiology", section on 'Leiomyoma'.)

●(See "Recurrent pregnancy loss: Management", section on 'Uterine abnormalities'.)

Indications for myomectomy during pregnancy — Given the potential for harm (hemorrhage, uterine rupture, miscarriage, or preterm delivery), myomectomy is avoided during pregnancy, especially if an intramyometrial incision is required, unless the procedure cannot be safely delayed [2,18,25,39,67-73]. Inability to control hemorrhage during myomectomy is a real possibility and may necessitate hysterectomy.

Rarely, myomectomy of pedunculated or subserosal fibroids has been performed antepartum for management of an acute abdomen or obstruction, and myomectomy may be required at cesarean delivery in order to close the hysterotomy [74,75].

A systematic review that included 97 patients who underwent myomectomy during pregnancy noted the following findings, although data were incomplete in several cases [75]:

●Abdominal pain was by far the most common preoperative symptom, reported by 80 percent of patients, and the most common indication for surgery. The second most common preoperative symptom was fever, which was observed in 12 percent of patients.

●The median gestational age at myomectomy was 16 weeks (range 6 to 26 weeks).

●Three-quarters of patients had removal of a single fibroid; the remainder had multiple fibroids removed.

●The majority of myomectomies (48/66 [73 percent]) were for pedunculated fibroids, but 26/66 (39 percent) cases were intramural.

●The median estimated blood loss was 350 mL (range 30 to 4500 mL). Five patients received transfusions.

●Postoperative outcomes included:

•Five miscarriages.

•Ninety-two ongoing pregnancies.

-The mean gestational ages at delivery for patients undergoing single versus multiple myomectomy were 37.2 and 36.8 weeks, respectively, and the cesarean delivery rates were 51 and 83 percent, respectively.

-Most ongoing pregnancies were uneventful. However, one patient developed full thickness myometrial necrosis with abscess formation and exposure of a 7 by 2 cm portion of the amniotic sac after resection of a degenerating pedunculated leiomyoma by monopolar diathermy at 17 weeks. Antibiotic therapy, abscess drainage, and repair of the defect were successful, allowing the patient to deliver at 37 weeks by planned cesarean.

Cesarean myomectomy is discussed below. (See 'Cesarean myomectomy' below.)

Painful fibroids — Pregnant women with painful fibroids may require hospitalization for pain management [2,37,46,48]. We suggest supportive care and administration of acetaminophen as the initial intervention.

Short-term use of opioids in standard doses or a short course (ideally <48 hours) of nonsteroidal anti-inflammatory drugs (NSAIDs) can be given when pain is not controlled by these measures. First-trimester opioid use has been associated with an increased risk of congenital anomalies in some studies, but the data are weak and do not justify withholding these medications when needed to control pain. (See "Inhibition of acute preterm labor", section on 'Fetal side effects'.)

Pain may be managed with a short course of ibuprofen [18] or indomethacin 25 mg orally every 6 hours for up to 48 hours [19]. NSAID therapy should be limited to pregnancies less than 32 weeks of gestation because of the possibility of inducing premature closure of the ductus arteriosus, neonatal pulmonary hypertension, oligohydramnios, and fetal/neonatal platelet dysfunction [19,76-78]. If the NSAID is continued for >48 hours, weekly sonographic assessment for oligohydramnios and narrowing of the fetal ductus arteriosus should be performed. If either of these findings is noted, the NSAID should either be discontinued or the dose reduced (eg, reduce indomethacin dose to 25 mg every 12 hours). Repeat courses can be given as needed for recurrent episodes of pain. Although first-trimester use of NSAIDs has been associated with miscarriage in some studies, the best data do not support an association [79]. (See "Inhibition of acute preterm labor", section on 'Cyclooxygenase inhibitors (eg, indomethacin)' and "Safety of rheumatic disease medication use during pregnancy and lactation", section on 'NSAIDs'.)

Case reports have described successful use of epidural analgesia for treatment of severe pain refractory to other therapies [80-82]. Fibroid-related pain is not an indication for emergency surgery; however, surgery can be considered if the pain cannot be adequately controlled by other means.

Fibroids prolapsing into the vagina — We generally advise against removal of prolapsed fibroids in pregnancy as the risks likely outweigh the benefits, unless there is an easily accessible pedunculated fibroid on a thin stalk. Removal may lead to hemorrhage, rupture of membranes, and/or pregnancy loss [83].

The need for resection should be assessed on a case-by-case basis. Clinically significant bleeding, excessive pain, urinary retention, and (rarely) infection during pregnancy due to a prolapsed fibroid are reasonable indications for resection.

Case reports have described generally successful transvaginal removal of symptomatic fibroids in pregnant women; heavy and/or persistent vaginal bleeding was the most common symptom prompting removal [83]. The procedure for transvaginal myomectomy depends on the origin of the fibroid (cervix versus submucosa) and thickness of the stalk/base, which can be determined clinically or by transvaginal ultrasound or magnetic resonance imaging, if necessary. (See "Uterine fibroids (leiomyomas): Prolapsed fibroids".)

An asymptomatic lower uterine segment submucosal prolapsed fibroid may become intrauterine with advancing gestation.

Route of delivery — Most women with fibroids will have a successful vaginal delivery and thus should be offered a trial of labor. Cesarean delivery is reserved for standard obstetric indications (eg, malpresentation, failure to progress).

Planned cesarean delivery may be considered because of concerns that fetal descent will be obstructed by a fibroid, but should be limited to women most likely to fail a trial of labor: those with large cervical fibroids or with lower uterine segment fibroids that distort the uterine cavity and are located between the fetal vertex and cervix in the third trimester [84].

Operative issues at cesarean delivery — Women with large, retroplacental or anterior lower uterine segment fibroids are at high risk of intrapartum or postpartum hemorrhage at the time of cesarean delivery, so appropriate preparations should be taken (see "Overview of postpartum hemorrhage", section on 'Planning'). Preoperative placement of bilateral iliac artery balloon catheters, use of a cell saver, and availability of blood products in a cooler should be considered on a case-by-case basis.

A vertical skin incision and a posterior or classical hysterotomy are sometimes necessary to obtain adequate exposure when the fibroids are located in the lower uterine segment. Every effort should be made to avoid transecting a fibroid during hysterotomy as the incision may be impossible to close without first removing the tumor. Ultrasound imaging can be used (either antepartum or intrapartum) to map out the optimal location for the hysterotomy incision at the time of cesarean in patients with large uterine fibroids. Intraoperatively, a sterile probe cover is placed on the ultrasound transducer and sterile gel is applied to the uterine serosa; the best incision site can then be mapped sonographically.

Cesarean myomectomy — Although we believe that cesarean myomectomy generally should be avoided, observational data suggest that it is possible without a high risk of life-threatening events as long as the surgeon has appropriate expertise, appropriate patients are selected (eg, symptomatic pedunculated fibroids), and blood products are available. This decision should be made with caution given the biases inherent to observational studies. We avoid intramyometrial myomectomy because of the risk of severe hemorrhage [2,67,85], which is more likely in pregnant women since the term uterus receives 17 percent of cardiac output.

In meta-analyses of mostly retrospective studies of patients with fibroids undergoing cesarean, those undergoing concomitant myomectomy had greater drops in hemoglobin (mean difference 0.25 to 0.27 mg/dL), an approximately 40 percent increase in use of blood transfusion, and longer hospital stay [86,87].

A limitation of the analyses is that results were not stratified according to the location and type of the myomas (eg, pedunculated, subserosal, intramural, submucosal), and these characteristics affect the risk of hemorrhage. For example, favorable results have been reported for removal of pedunculated fibroids at the time of cesarean delivery. In a series of five myomectomies performed during cesarean, the four pedunculated fibroids were removed without difficulty, while removal of the single nonpedunculated fibroid was associated with severe hemorrhage [48]. (See "Uterine fibroids (leiomyomas): Open abdominal myomectomy", section on 'Procedure'.)

Management of patients with prior myomectomy

Route of delivery and timing of scheduled cesarean delivery — Timing and route of delivery must be individualized based on the degree and location of the prior uterine surgery, as described in the operative report. In the absence of strong evidence of the absolute risk of rupture [88], we take a conservative approach and suggest cesarean delivery prior to the onset of labor in patients who underwent an extensive or complicated myomectomy, similar to patients who have had a previous classical cesarean delivery. Such patients are delivered at 36+0 to 37+0 weeks of gestation since they appear to be at risk for preterm labor [34], whereas patients with less extensive prior surgery may be delivered as late as 38+6 weeks [89]. Merely entering the uterine cavity does not constitute an extensive myomectomy, which may be considered a myomectomy in which extensive or complete invasion of the myometrium is required for removal of one or several intramural or submucosal fibroids of appreciable size, followed by extensive uterine reconstruction [90,91]; however, there is no standard definition.

For patients who have had an intramyometrial myomectomy that was unlikely to have significantly compromised the myometrium, we suggest a trial of labor with continuous intrapartum fetal monitoring, early access to obstetric anesthesia, and the ability to perform an emergency cesarean delivery, if it becomes necessary. Patients who have had a pedunculated fibroid removed would not be expected to have compromised the integrity of the myometrium and do not require special monitoring during labor.

The magnitude of the risk of uterine rupture in pregnancies after myomectomy and specific criteria associated with increased risk are difficult to ascertain because of the small number of cases reported and lack of detail about the operative procedures performed. Available data, although limited, suggest that the risk of uterine rupture after myomectomy is not significantly greater than that for a patient attempting trial of labor after cesarean. In a 2016 systematic review of studies with at least five cases of pregnancy after myomectomy, the overall incidence of uterine rupture after myomectomy was 7/756 or 0.93 percent (95% CI 0.45-1.92 percent) [92]. The incidence was 0.47 percent (2/426, 95% CI 0.13-1.70 percent) in women undergoing trial of labor after myomectomy and 1.52 percent (5/330, 95% CI 0.65-3.51 percent) in women before the onset of labor; this difference was not statistically significant. Six of the seven ruptures occurred in women who had a prior laparoscopic myomectomy, which has been attributed to the technical challenge of laparoscopic suturing [93,94]. All ruptures occurred following myomectomy of an intramural fibroid, although this was not noted to be a significant risk factor for uterine rupture. The uterine cavity was not entered during myomectomy in three cases; this information was not available in the other four cases. The ruptures occurred at 24 (twins), 25, 30, 32, 36, 37, and 40 weeks of gestation; however, this finding may be biased by scheduled cesarean deliveries at term.

Abnormal placentation — Prior hysteroscopic removal of a submucosal fibroid may increase the risk of abnormal placentation, especially placenta accreta. Although the risk of placenta accreta after prior myomectomy appears to be low [95,96], data are sparse. We suggest ultrasound screening for possible placenta accreta in the late second or early third trimester. (See "Placenta accreta spectrum: Clinical features, diagnosis, and potential consequences".)

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: Uterine fibroids (leiomyomas)".)

SUMMARY AND RECOMMENDATIONS

●The pattern of fibroid growth during pregnancy is probably not linear: Most of the growth occurs in the first trimester, with little if any further increase in size during the second and third trimesters. (See 'Change in size during pregnancy and postpartum' above.)

●Most pregnant women with fibroids do not have any complications during pregnancy related to the fibroids. When complications occur, pain is the most common complication. The frequency of pain correlates with increasing fibroid size. (See 'Complications' above and 'Degeneration and torsion' above.)

Size and location appear to be risk factors for pregnancy complications: large size (>3 cm), retroplacental location, and/or distortion of the uterine cavity are characteristics that have been associated with an increased risk of miscarriage, placental abruption, fetal growth restriction, hemorrhage, and preterm labor and birth. The presence of multiple fibroids is another risk factor for preterm labor and birth. (See 'Complications' above.)

●Every effort should be made to avoid surgical removal of fibroids in pregnancy because of the risk of significant morbidity (hemorrhage). Myomectomy is performed if the procedure cannot be safely delayed. (See 'Indications for myomectomy during pregnancy' above and 'Cesarean myomectomy' above.)

●Prior hysteroscopic removal of a submucosal fibroid may increase the risk of abnormal placentation, especially placenta accreta. Although the risk of placenta accreta after prior myomectomy appears to be low, we suggest ultrasound examination for possible placenta accreta in the late second or early third trimester. (See 'Abnormal placentation' above.)

●For pregnant women with painful fibroids, we suggest supportive care and administration of acetaminophen as the initial intervention. Short-term use of opioids in standard doses or a short course of nonsteroidal anti-inflammatory drugs can be given when pain is not controlled by these measures. (See 'Painful fibroids' above.)

●For pregnant women with a prolapsed fibroid, clinically significant bleeding, excessive pain, urinary retention, or infection is a reasonable indication for resection. (See 'Fibroids prolapsing into the vagina' above.)

●Cesarean delivery is performed for standard obstetric indications (eg, malpresentation, failure to progress), including obstruction of the birth canal by a fibroid. (See 'Route of delivery' above.)

●If the uterine cavity was entered during a prior myomectomy or a large number of myomas were removed, we suggest scheduled cesarean delivery rather than a trial of labor (Grade 2C). In the absence of these criteria, we manage patients with a prior myomectomy similar to women who have had a prior cesarean delivery. (See 'Management of patients with prior myomectomy' above.)

Scheduled cesarean delivery is performed between 37+0 and 38+6 weeks of gestation, although consideration of delivery as early as 36 weeks is reasonable for women with prior extensive myomectomy (analogous to a patient with prior classical hysterotomy).

●Every effort should be made to avoid cutting through fibroids at cesarean delivery as it can be impossible to close the hysterotomy site if the fibroids are in it. Intraoperatively, a sterile probe cover can be placed on the ultrasound transducer and sterile gel applied to the uterine serosa; the best incision site can then be mapped sonographically. (See 'Route of delivery' above.)