Number and size of uterine fibroids and obstetric outcomes.

OBJECTIVE: Estimating the impact of sonographically identified multiple or large (≥5 cm in diameter) fibroids on obstetric outcomes.

METHODS: Retrospective cohort study of 219 women with uterine fibroids (identified on a routine second-trimester ultrasound survey over a 3-year period, 2010-2012) and their age-matched controls. Inclusion criteria were singleton pregnancy, delivery at >24 weeks of gestation and no pathological conditions (chronic hypertension, gestational diabetes or pre-existing diabetes mellitus, uterine anomalies or fetal malformations).

RESULTS: Compared to women with no fibroids, women with multiple fibroids (n = 34) had a significantly higher rate of preterm birth (29.4% versus 5%, p < 0.001), cesarean section (73.5% versus 37%, p < 0.001) and breech presentation (11.8% versus 2.7%, p = 0.04). Women with large fibroids (n = 48) had a higher rate of preterm birth (16.7% versus 5%, p = 0.01) and pPROM (10.4% versus 0.5%, p < 0.001). By multivariate analysis, only multiple fibroids and previous preterm birth showed an independent significant association with preterm birth (OR = 7.37, 95% CI 2.50-21.68 and OR = 13.01, 95% CI 3.56-47.52, respectively).

CONCLUSIONS: Women with uterine fibroids are at an increased risk of obstetric complications. In particular, multiple rather than large fibroids are associated with a significantly increased risk of preterm birth and cesarean delivery while large fibroids are associated with a higher risk of pPROM. No correlation with IUGR, placenta previa or placental abruption was found.