Fetus
Poster Session 2
Taylor S. Freret, MD
Massachusetts General Hospital
Cambridge, MA, United States
Anjali J. Kaimal, MD (she/her/hers)
Professor and Vice Chair of Clinical Operations, Department of OBGYN
University of South Florida Morsani College of Medicine
Tampa, FL, United States
Alexander Melamed, MD, MPH
Massachusetts General Hospital
Boston, MA, United States
.jpg "Mark A. Clapp, MD, MPH (he/him/his) photo")
Mark A. Clapp, MD, MPH (he/him/his)
Massachusetts General Hospital
Boston, MA, United States
In 2020, SMFM recommended 37-week delivery for severe fetal growth restriction (FGR). We sought to determine if this recommendation resulted in national practice changes.
Study Design:
This repeated cross-sectional analysis used US natality data of singletons at ≥37 weeks completed gestation in the US between May 2019 and Oct 2021. Exclusion criteria included hypertension, diabetes, or fetal anomalies. The FGR cohort included birthweight < 3rd percentile by gestational age (a proxy for severe FGR); a control cohort included birthweight >10th percentile. A population-level linear regression difference-in-differences (DID) analysis was performed. The primary outcome was 37-week delivery rate. Other secondary outcomes included 37-week induction, cesarean delivery, NICU admission, respiratory support, and perinatal death. The time between online and in print publication (May-Oct 2020) was excluded. The pre-period was from May 2019-Apr 2020; the post-period from Nov 2020-Oct 2021.
Results:
The study included 5,975,195 patients; 2,464,143 in the pre-period and 2,308,719 in the post-period. After the guidelines were disseminated, the rate of 37-week delivery increased in the FGR group relative to the non-FGR group (DID estimate: 1.59 percentage points, 95% CI 1.06-2.13, p< 0.001), an increase from 11.3% (expected delivery rate in the FGR cohort) to 12.8% (observed). Induction of labor at 37 weeks also increased (DID estimate: 1.10 pp, 95% CI 0.73-1.47, p< 0.001). There was a slight increase in the need for respiratory support (DID estimate: 0.25 pp, 95% CI 0.005-0.49, p=0.046), but no change in cesarean delivery, neonatal respiratory support, or perinatal death (Table).
Conclusion:
SMFM recommendations for severe FGR led to increased 37-week delivery, although absolute rates remained low, suggesting many fetuses may not be diagnosed antenatally. There was a slight increase in need for respiratory support but no change in the rate of cesarean delivery or NICU admission. It is hard to assess changes in perinatal death given limited sample size and inability to know which fetuses were diagnosed antenatally.