Uterine myomas: effect of prior myomectomy on pregnancy outcomes

Reproductive aged women with fibroids must weigh the risks and benefits of preconception myomectomy. Women with fibroids may have higher rates of fetal growth restriction (FGR) and stillbirth; however, there is a paucity of data on the impact of myomectomy on pregnancy outcomes. We compared perinatal outcomes in women with prior myomectomy versus those with no prior myomectomy and at least one fibroid ≥ 5 cm.

Retrospective cohort study of women at a single center who delivered between 2008 and 2017 with a viable intrauterine pregnancy at initial ultrasound scan and either prior myomectomy, or, in the no-myomectomy cohort, at least one fibroid ≥ 5 cm on a prenatal scan performed at < 21 weeks' gestation (wga). Pregnancies complicated by major congenital anomalies were excluded. Primary outcome was preterm birth (PTB) < 37wga. Secondary outcomes included rates of spontaneous loss, cesarean delivery (CD), abnormal placentation, malpresentation, FGR, birthweight, birthweight percentile, estimated blood loss (EBL), blood transfusion, and neonatal survival to discharge.

A total of 290 women met inclusion criteria: 70 had a prior myomectomy, 220 women had ≥1 fibroid ≥5cm. Women with prior myomectomy were older, more likely to have private insurance, and more likely used artificial reproductive technology to conceive; 20% with prior myomectomy still had at least one ≥ 5 cm myoma on their obstetric scan. Rates of spontaneous loss were lower in the prior myomectomy group (1.4% vs 7.3%; p = .08). Of the 273 pregnancies continuing beyond 20 weeks, women with prior myomectomy had significantly more PTBs (35% vs. 21%, p = .02) and significantly different primary birth indications (p < .0001). However, after controlling for late preterm, prelabor cesareans recommended by providers in the myomectomy cohort, the difference in PTB rates was not significant (p = .13). The myomectomy group had more CDs (88% vs. 53%, p < .0001), higher EBL (1250 mL vs. 811 mL, p = .04), and a trend toward more blood transfusions (16% vs 8%, p = .05). Other selected outcomes were similar, including rates of FGR.

Women with prior myomectomy had significantly more PTBs, due in part to more preterm, prelabor cesareans in the late preterm period. Otherwise, prior myomectomy did not confer appreciable obstetric or perinatal benefits, as patients had more CDs, and higher EBL. Recommendations to perform preterm prelabor cesareans in this population may explain some of the PTB disparity. The effect of prior myomectomy on early pregnancy loss and infertility requires further study.