Malperfusion as a possible mechanism of preterm labor in patients with uterine anomalies

Abstract

Congenital uterine anomalies have been associated with infertility and increased risk of miscarriage, IUGR and preterm birth. While those could be caused by restricted expansion of an abnormal endometrial cavity, an alternative explanation could be an abnormal placental implantation. Our objective was to examine clinical and histopathologic factors associated with preterm delivery in a large cohort of pregnancies in women with Mullerian anomalies. Retrospective cohort study. Singleton pregnancies in women with uterine anomalies (diagnosed on MRI and HSG) who received obstetrical care at our institution from 2007-2012 were retrospectively identified. Student t test and ANOVA were used to compare continuous, and Fisher's exact test to compare categorical outcomes. 111 pregnancies in 85 women were included. There were 42 pregnancies with bicornaute, 24 with unicornuate, 24 with septate, 19 with didelphys and one each with arcuate and T-shaped uterus. 24.3% of pregnancies were delivered prior to term. There was no significant association between gestational age at delivery and type of uterine anomaly (p=0.4). Of 27 preterm deliveries, only 14 (52%) were due to preterm labor or PPROM. Histological evidence of placental malperfusion was present in 22% of all pregnancies, and those delivered at earlier mean gestational age (35.5 ± 3.1 vs. 37.3 ± 2.1 weeks; p=0.03). Malperfusion was more common in preterm than in full term births (41% vs. 14%; p=0.04). Conversely, inflammation was not more common in preterm compared to term deliveries (18% vs. 17%; p=1.0). While ascending genital tract infection leading to inflammation is generally considered a proximate cause of preterm birth, malperfusion was more commonly associated with preterm births in women with uterine anomalies. These findings could indicate that abnormal placental implantation may be a more significant factor for prematurity than mechanical/inflammatory factors in women with congenital uterine anomalies.