How do bicornuate uteri alter pregnancy, intra-partum and neonatal risks? A population based study of more than three million deliveries and more than 6000 bicornuate uteri

Objectives: To explore maternal and neonatal outcomes in pregnant women with bicornuate uteri.

Methods: Retrospective population-based cohort study utilizing data from the Healthcare-Cost and Utilization Project-Nationwide Inpatient Sample (HCUP-NIS) from 2010 to 2014. There were 3,846,342 births between 2010 and 2014, included in the study. Six thousand and 195 deliveries were to women with bicornuate uterus. The remaining deliveries without other uterine anomalies were categorized as the reference group (n=3,840,147).

Results: Pregnant women with bicornuate uterus were older and more likely to be obese (p=0.0001) with previous cesarean deliveries (CD) (31 vs. 17.1%, p=0.0001). After adjustment for confounders, they were more likely to experience pregnancy-induced hypertension (HTN) (aOR 1.21, 95%CI: 1.1-1.3), p=0.0001), preeclampsia (aOR 1.4, 95%CI: 1.2-1.6, p=0.0001) and placenta previa (aOR 1.7, 95%CI: 1.3-2.2, p=0.0001). Moreover, they were more likely to deliver preterm (aOR 2.8, 95%CI: 2.6-3.1, p=0.0001), deliver by CD (aOR 5, 95%CI: 3.1-4.1, p=0.0001), experience preterm pre-labor rupture of membranes (PPROM) (aOR 3.5, 95%CI: 2.6-3.1, p=0.0001), and have a placental abruption (aOR 3.0, 95%CI: 2.5-3.5, p=0.0001). There were increased risks of PPH (aOR 1.4, 95%CI: 1.2-1.6, p=0.0001), wound-complications (aOR 2.0, 95%CI: 1.5-2.7, p=0.0001), hysterectomy (aOR 2.6, 95%CI: 1.6-4.1, p=0.0001), blood-transfusion (aOR 1.7, 95%CI: 1.5-2.1, p=0.0001), and DIC (aOR 1.6, 95%CI: 1.1-2.5), p=0.014) in the group with bicornuate uteri. Also there was higher risk of SGA (aOR 2.9, 95%CI: 2.6-3.2, p=0.0001) and IUFD (aOR 2.5, 95%CI: 1.8-3.3, p=0.0001).

Conclusions: Bicornuate uteri can increase risks in pregnancy by many folds. Particularly risks of: premature delivery, CD, PPROM, placental abruption, hysterectomy, SGA and IUFD were increased 250-500%.