(433) Does the Timing of Resolution of Low Placentation Affect the Risk of Postpartum Hemorrhage?

Low placentation, defined as placenta previa or low-lying placenta, is associated with increased risk of postpartum hemorrhage (PPH), both if resolved antepartum or persistent until delivery. This study investigates whether the gestational age (GA) at which low placentation resolves is associated with increased odds of PPH.

Study Design:

Retrospective cohort included patients who delivered at Mount Sinai Hospital from 2015-2019 and were diagnosed with low placentation via transvaginal ultrasound at second-trimester anatomical survey. Study subjects were divided into two groups based on GA at detection of low placentation resolution: early resolution (≤28 weeks GA) and late resolution ( >28 weeks GA).  Primary outcome was PPH, secondary outcomes included use of uterotonics or hemostatic procedures, blood transfusion, and ICU admission. Outcomes were analyzed using multivariable logistic or linear regression, adjusting for age, body mass index, use of in vitro fertilization, original low placentation diagnosis (previa vs low-lying), placental location at time of diagnosis, and uterine surgical history.

Results:

634 patients were included, 454 in the early and 180 in the late resolution group. Demographics and risk factors were similar between cohorts, except late resolution cohort had a greater percentage of placenta previa (as opposed to low-lying placenta) at diagnosis (36% vs 25%, p=0.006), and increased proportion of Black and Hispanic persons (p=0.027). There was no significant difference in odds of PPH amongst the early compared to late resolution group (aOR 1.61, 95% CI 0.90-2.82). When assessed continuously, there was no association between GA at resolution and odds of PPH (aOR 1.06, 95% CI 0.97-1.16). There was no significant difference in the secondary outcomes.

Conclusion: Our analysis demonstrated no significant effect of GA at observation of low placentation resolution on the risk of PPH in a large, diverse, urban cohort. Future prospective studies, with more frequent placental surveillance, will be important in determining the impact of timing of low placentation resolution on risk of PPH.