Subchorionic hematomas in the first trimester were not associated with adverse pregnancy outcomes after 20 weeks’ gestation in singleton pregnancies, according to Mackenzie N. Naert of the Icahn School of Medicine at Mount Sinai, New York, and associates.

The investigators conducted a retrospective study, published in Obstetrics & Gynecology, of all women who presented for prenatal care before 14 weeks’ gestation at a single maternal-fetal medicine practice between January 2015 and December 2017. Of the 2,172 women with singleton pregnancies included in the analysis, 389 (18%) had a subchorionic hematoma.

Women with subchorionic hematomas were more likely to have their first ultrasound at an earlier gestational age (8 5/7 weeks vs. 9 6/7 weeks; P less than .001) and to have vaginal bleeding at the time of the ultrasound exam (32% vs. 8%; P less than .001). No other differences in baseline characteristics were observed, and after univariable analysis, subchorionic hematoma was not associated with any of the measured adverse outcomes, such as preterm birth, low birth weight, preeclampsia, gestational hypertension, placental disruption, intrauterine fetal death, cesarean section, blood transfusion, or antepartum admission.

In a regression analysis that included subchorionic hematoma, vaginal bleeding, and gestational age at ultrasound examination, vaginal bleeding had an independent association with preterm birth at less than 37 weeks’ gestation (adjusted odds ratio, 1.8; 95% confidence interval, 1.2-2.6) and birth weight less than the 10th percentile (aOR, 1.8; 95% CI, 1.2-2.6). No independent association was found for subchorionic hematoma.

“Most subchorionic hematomas present during the first trimester resolved by the second trimester,” the investigators wrote. “Therefore, women diagnosed with a first-trimester subchorionic hematoma should be reassured that their rate of adverse pregnancy outcomes at more than 20 weeks of gestation is not affected by the presence of the subchorionic hematoma. Additionally, we have previously shown that first-trimester subchorionic hematoma is not associated with pregnancy loss at less than 20 weeks of gestation.”

The authors reported no conflicts of interest.

SOURCE: Naert MN et al. Obstet Gynecol. 2019 Sep 10. doi: 10.1097/AOG.0000000000003487.