Abstract
Objective: Nonimmune hydrops fetalis (NIHF) is associated with poor perinatal outcomes including preterm birth (PTB). However, the frequency and causes of PTB in this population are not well understood. We hypothesized that NIHF frequently results in PTB due to medically indicated delivery for fetal distress. Study Design: This was a secondary analysis of a prospectively enrolled cohort of pregnancies with NIHF that underwent exome sequencing if standard testing was non-diagnostic. The primary outcome was frequency of PTB at <37 weeks’ gestation. Secondary outcomes were reasons for PTB, fetal predictors of PTB, and frequency of neonatal death following PTB. Results: Fifty-six cases were included, with a median gestational age at delivery of 32.8 weeks (IQR 30.3-35.0). Overall, 86% (48/56) were delivered preterm. Among 48 PTBs, 18 (38%) were spontaneous, 9 (19%) were medically indicated for maternal indications (primarily preeclampsia), and 21 (44%) were medically indicated for fetal indications (non-reassuring antenatal testing or worsening effusions). Neither fetal genetic diagnosis nor polyhydramnios were associated with PTB. Conclusion: More than four fifths of pregnancies with NIHF result in PTB, often due to non-reassuring fetal status. These data are informative for counseling patients and for developing strategies to reduce PTB in pregnancies with NIHF.
