Obstetric outcomes in pregnancies with solitary huge uterine fibroids: size versus type and location

Huge uterine fibroids represent a rare but clinically significant complication of pregnancy. This study aimed to evaluate their impact on major obstetric outcomes and to determine whether fibroid type and anatomical location modify these risks. This retrospective observational study (2010-2023) compared 64 singleton pregnancies complicated by a single huge uterine fibroid (maximal diameter ≥ 10 cm) with 128 matched fibroid-free controls. Fibroids were classified sonographically by type and location. Outcomes included mode of delivery, gestational age (GA) at birth, preterm birth (PTB), neonatal birthweight, 5 min Apgar and maternal hemoglobin decline. Multivariable logistic regression was used to identify independent predictors of cesarean delivery (CS). Among 57,200 pregnancies, huge uterine fibroid was identified in approximately 1 in 670 pregnancies (0.15%). These pregnancies were associated with higher rates of CS compared with controls (39.1% vs. 8.6%, P < 0.01), earlier GA (median 38.0 vs. 39.6 weeks, P < 0.01), a markedly increased rate of PTB (29.7% vs. 4.7%, P < 0.01), and greater maternal hemoglobin decline. Within the fibroid cohort, fibroid size relative to the median diameter was not associated with adverse outcomes. In contrast, intramural fibroids were strongly associated with both earlier GA and an increased risk of CS compared with subserosal lesions (adjusted OR 23.79, 95% CI 3.67-534.32, P < 0.01). Fibroids located in the lower uterine segment or cervix were also associated with elevated CS rates. Obstetric risk of pregnancies complicated by a huge solitary fibroid is driven primarily by fibroid type and anatomical location rather than size alone, supporting individualized counseling and delivery planning.