Uterine Fibroids in Pregnancy: Maternal, Obstetric, and Neonatal Outcomes in a Retrospective Cohort Study.

Background: Uterine fibroids are the most common benign tumors in women of reproductive age, and their coexistence with pregnancy is becoming increasingly frequent as maternal age at first pregnancy rises. Objective: The objective of this study was to evaluate the impact of uterine fibroids on obstetric and neonatal outcomes and, secondarily, the effect of pregnancy on fibroid growth. Study Design: This retrospective observational study included 1512 pregnant women, 136 of whom had uterine fibroids, who were followed at a university hospital. Ultrasound examinations were performed before pregnancy (T0) and during the first (T1), second (T2), and third (T3) trimesters. Fibroid number, size, location, and ultrasound characteristics according to FIGO classification were recorded. Obstetric complications, mode of delivery, and neonatal outcomes were analyzed according to fibroid type and size. Fibroid growth throughout pregnancy was also evaluated. Results: Among 1512 pregnant women followed between 1 January 2024 and 30 November 2025, 136 patients (9.0%) had uterine fibroids. A positive family history of fibroids was identified in 36% of cases. Gestational complications were infrequent overall, although gestational hypothyroidism was significantly more common among women with fibroids, whereas preeclampsia and postpartum hemorrhage were significantly less frequent in univariable analysis. Vaginal delivery was less frequent in the fibroid group, while operative vaginal delivery and cesarean section were significantly more common. Fetal growth restriction (FGR) and umbilical venous pH also differed significantly between groups. In multivariable analysis adjusted for maternal age, BMI, parity, ART, smoking, chronic hypertension, and diabetes, the association with cesarean section was attenuated (aOR 1.47, 95% CI 0.93-2.32), whereas lower PPH rates persisted (aOR 0.34, 95% CI 0.14-0.84) and a slight inverse association with umbilical venous pH remained detectable (β -0.01, p = 0.01). Exploratory stratification according to FIGO classification (3-4 vs. 5-7) showed significant differences in PPH, cesarean section, FGR, and LGA. Repeated-measure analysis demonstrated progressive fibroid growth in maximum diameter during pregnancy compared with preconceptional measurements (T0) (p < 0.001), with substantial enlargement already observed by the second trimester and fibroids ≤5 cm exhibiting greater relative growth at T2 compared with T0 than larger lesions (+18% vs. +7%; p = 0.03). Conclusions: Uterine fibroids were not consistently associated with adverse obstetric or neonatal outcomes, although careful obstetric surveillance remains warranted. Pregnancy was associated with progressive fibroid growth, particularly in smaller lesions and during early gestation.