Resolution of low-lying placenta and placenta previa is associated with increased risk of postpartum hemorrhage

OBJECTIVE To determine if women who experience resolution of low-lying placenta and placenta previa are at increased risk of postpartum hemorrhage compared to those with normal placentation throughout pregnancy. METHODS Retrospective cohort study including women who delivered at Mount Sinai Hospital between 2015 and 2019, diagnosed with low-lying placenta or placenta previa using transvaginal ultrasound at the time of second trimester anatomical survey with resolution of low placentation on subsequent ultrasound. Women undergoing second trimester anatomical survey diagnosed with normal placentation using transvaginal ultrasound were randomly identified for comparison. The primary outcome was rate of postpartum hemorrhage. Secondary outcomes included need for blood transfusion, use of additional uterotonic medication, need for additional procedures to control bleeding and maternal ICU admission. Outcomes were assessed using a multivariable logistic regression model. RESULTS 1,256 women were identified for analysis, 628 in the resolved low placentation cohort and 628 in the normal placentation cohort. Resolved low placentation was associated with commercial health insurance (p=0.04), older maternal age (mean age 33 ± 5.4 vs. 31.5 ± 5.8), lower BMI (mean BMI 27.9 ± 5.5 vs. 30.3 ± 6.0), use of in vitro fertilization, Non-Hispanic White race, and posterior placental location (all p<0.01). Patients with resolved low versus normal placentation had greater odds of postpartum hemorrhage (adjusted OR 3.5, 95% CI 2.0-6.0; p<0.01), additional uterotonic use (adjusted OR 2.2, 95% CI 1.5-3.1; p<0.01) and increased rates of additional procedures to control bleeding (adjusted OR 4.0, 95% CI 1.2-11.9; p=0.01). CONCLUSIONS Despite high rates of resolution of low-lying placentas and placenta previas at term, women with resolved low placentation remain at increased risk of postpartum hemorrhage compared to those with normal placentation throughout pregnancy. This article is protected by copyright. All rights reserved.