Twin pregnancy in patients with a uterine anomaly

Objective: In singleton pregnancies, a uterine anomaly is a known risk factor for preterm birth and fetal growth restriction. Data on outcomes of twin pregnancies with uterine anomalies is limited to case reports. The objective of this study was to compare outcomes in twin pregnancies based on the presence or not of a uterine anomaly. Methods: This was a retrospective cohort of twin pregnancies managed by a single maternal-fetal medicine practice from 2005 to 2012. Patients with monoamniotic twins and twin-twin transfusion syndrome were excluded. Pregnancy outcomes were compared between patients with and without a uterine anomaly. Nonparametric tests (Fisher's exact test, Mann-Whitney U) were used for analysis. A p value of ≤0.05 was considered significant. Results: Five hundred and fifty-six twin pregnancies were included, 17 (3.1%) of whom had a known uterine anomaly (nine septate uterus, three bicornuate, three arcuate, one unicornuate and one didelphys). Patients with a uterine anomaly had significantly worse outcomes, including cerclage, preterm birth and lower median birth weights. Birth weight less than the 10th or 5th percentile for gestational age was not more common in patients with a uterine anomaly, nor was there an increase in birth weight discordancy. Conclusion: In patients with twin pregnancies, the presence of a uterine anomaly is associated with an increased risk of cerclage, preterm birth and lower birth weights, but not fetal growth restriction.