Questions and answers from SMFM about the implications of uterine fibroids during pregnancy
Dr. Kase is a Maternal-Fetal Medicine physician at Tripler Army Medical Center, Honolulu, Hawaii.
Dr. Blackwell is Professor and Chair of the Department of Obstetrics, Gynecology & Reproductive Sciences at the University of Texas Health Science Center at Houston.
Neither author has a conflict of interest to report with respect to the content of this article.
Q. A 32-year-old G1P0 is reported to have 3 uterine fibroids at the time of her 20-week anatomy ultrasound, including one measuring 6x6x8 cm. How common are fibroids in pregnancy, and how should women be counseled regarding the impact of uterine fibroids on pregnancy?
A. Uterine fibroids are the most common benign gynecologic tumors, and are found in 1% to 10% of women during prenatal ultrasound screening. Incidence of fibroids noted during second-trimester ultrasound was reported to be 3% in a large single-institution cohort study in St. Louis, Missouri, that involved approximately 64,000 women.1 In this same study population, the authors found that women with fibroids were an on average older (35 vs 30 years old), more likely to be African-American (34.5% vs 20.3%), and more likely to have additional comorbid medical conditions (eg, higher body mass index, diabetes, and chronic hypertension) when compared with those without fibroids. In another large cohort study in San Francisco, California, Qidwai et al noted that the prevalence of fibroids was 3.3% among African-Americans, 2.2% among Asians, 1.9% among whites, and 1.4% among Latinas.2
The potential impact of fibroids on pregnancy has been evaluated in numerous studies and are summarized in a recent systematic review.3 Women with uterine fibroids are more likely have pregnancies complicated by fetal malpresentation, preterm birth, preterm premature rupture of membranes (PPROM), placenta previa, placental abruption, cesarean delivery, and severe postpartum hemorrhage. The Table summarizes the rates of these outcomes for 2 large recent cohorts.1,2 In addition, neonatal birth weight at delivery was lower in women with fibroids compared to women without fibroids, although the likelihood of fetal growth restriction was similar among those with and without fibroids.4
Q. How do the size, number, and location of fibroids influence the obstetric outcome?
A. In their evaluation of more than 15,000 women with singleton pregnancy who underwent sonographic examination in the second trimester, Qidwai et al noted that 10% of those with fibroids had tumors that measured at least 10 cm.2 For women with fibroids >10 cm, there was an increased rate of malpresentation but no differences in preterm birth, PPROM, placenta previa, placental abruption, cesarean delivery, or postpartum hemorrhage (compared to those with fibroids < 10 cm). Stout et al noted that the rate of breech presentation was greater if the mean uterine fibroid volume was ≥ 100 mm.3 Other investigators have reported an association with greater risk of adverse obstetrical outcomes based on the size of fibroids (increased if > 5 cm). 5
The majority of women with fibroids have only one fibroid on ultrasound imaging, but up to 22% will have 4 or more fibroids. In the studies by both Qidwai et al and Stout et al the peripartum outcomes did not differ for women with one or multiple fibroids (Table). The location of the fibroid also did not influence the obstetric outcomes.1,2 The likelihood of breech presentation and of cesarean delivery was similar regardless of whether the fibroid was in lower uterine segment. In addition, Stout et al reported that the complications did not differ among cohorts whether the fibroid and placenta were in the same location or in different locations.1
NEXT: What is the natural history of fibroids in pregnancy?
Q. What is the natural history of fibroids in pregnancy?
A. Most fibroid growth occurs in the first trimester. Throughout pregnancy approximately 60% of fibroids will increase or decrease by greater than 10% of their original size.6 Hammoud et al found that in the first half of pregnancy 55.1% of fibroids decreased in size (mean decrease in volume 35%) while 44.9% enlarged (mean increase in volume 69%). They also noted that in later pregnancy most fibroids (75%) became smaller (mean decrease in volume 30%).7 Ultrasound evaluation during the postpartum period shows that a considerable percentage of fibroids (~36%) that presented in early pregnancy will have resolved and another 76% will have reduced in size.8
Q. What therapies are available for fibroid-related pain during pregnancy?
A. Fibroid-related pain requiring medications occurs in 5%–15% of women with fibroids. Use of nonsteroidal anti-inflammatory analgesic medications may be required and indomethacin (25 mg–50 mg by mouth every 6 hours for up to 48 hours) is a treatment option.9 Pain that does not improve within 48 hours of medical treatment should prompt the clinician to search for alternative etiologies. Prostaglandin synthase inhibitors should generally be avoided beyond 32 weeks’ gestation or restricted for use to fewer than 48 hours due to potential for fetal complications such as oligohydramnios and premature constriction of the ductus arteriosus.10-11
Q. For women with prior myomectomy, what is the recommended mode and timing of delivery in the current pregnancy?
A. One of the primary concerns regarding risks associated with prior myomectomy is uterine rupture either before or during labor.12 When evaluating the risk of uterine rupture, the extent of the uterine incision(s) as well as the size and number of myomas removed should be considered.13 In a report of 412 women with a pregnancy after myomectomy at a teaching institution in Nigeria, the incidence of uterine rupture was 0.2%.14 In a recent review of 176 singleton births after myomectomy, investigators noted that there were no cases of uterine rupture, including 35 women who underwent a trial of labor after both a prior myomectomy and a prior cesarean delivery.15 Information about the extent of the uterine dissection during the preceding myomectomy was not available for these patients.
Increasing rates of minimally invasive procedures add to the lack of clarity regarding the optimal timing and mode of delivery for women with a prior myomectomy. In a retrospective analysis, pregnancies following myomectomy at a single institution over 16 years were reviewed.16 Among 112 pregnancies with complete data, one case of uterine rupture occurred at 36 weeks’ gestation in a woman who had undergone a prior laparoscopic myomectomy.
Due to limited data, definitive recommendations regarding the appropriate route and timing of delivery in women with prior myomectomy are not practical. Patients should be counseled about the lack of data and potential for rupture. Plans should be individualized based on the type and extent of the myomectomy surgery. Until more and better data are available, a plan for labor and vaginal delivery is reasonable in women who did not have extensive myometrial dissection or entry into the endometrial cavity. Alternately, for those who choose an approach for scheduled cesarean delivery, timing at 37–38 weeks’ gestation is reasonable.17
To download a PDF of the patient education handout "Fibroids in Pregnancy: What You Need to Know," go to www.contemporaryobgyn.net/fibroids-in-pregnancy.pdf.
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2. Qidwai GI, Caughey AB, Jacoby AF. Obstetric outcomes in women with sonographically identified uterine leiomyomata. Obstet Gynecol. 2006;107:376–382.
3. Klatsky PC, Tran ND, Caughey AB, Fujimoto VY. Fibroids and reproductive outcomes: a systematic literature review from conception to delivery. Am J Obstet Gynecol. 2008;198(4):357–366.
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8. Laughlin SK, Herring AH, Savitz DA, et al. Pregnancy-related fibroid reduction. Fertil Steril. 2010;94:2421–2423.
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16. Kelly BA, Bright P, Mackenzie IZ. Does the surgical approach used for myomectomy influence the morbidity in subsequent pregnancy? J Obstet Gynaecol. 2008;28:77–81.
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