Understanding Preterm Birth in Pregnancies Complicated by Nonimmune Hydrops Fetalis

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.

Maternal outcomes of a cohort of pregnancies affected by non‐immune hydrops fetalis

“…Our stillbirth rate of 52% compared with 14%–31% in larger cohorts of prenatal NIHF 2,18 may be due to our strict NIHF definition and exclusion of non‐genetic etiologies. Our finding that most (73%) NIHF live births occurred preterm is consistent with published literature 2,8 . Our predominance of indicated preterm delivery (82%) for fetal indications (78%) in NIHF pregnancies is concordant with a recent study where 63% of preterm deliveries in NIHF pregnancies were indicated, 70% for fetal indications 8 .…”

“…Our finding that most (73%) NIHF live births occurred preterm is consistent with published literature 2,8 . Our predominance of indicated preterm delivery (82%) for fetal indications (78%) in NIHF pregnancies is concordant with a recent study where 63% of preterm deliveries in NIHF pregnancies were indicated, 70% for fetal indications 8 . Possible explanations include increased surveillance and advances in neonatal care 8 .…”

“…for fetal indications (78%) in NIHF pregnancies is concordant with a recent study where 63% of preterm deliveries in NIHF pregnancies were indicated, 70% for fetal indications. 8 Possible explanations include increased surveillance and advances in neonatal care. 8 Almost 75% of live births were cesarean deliveries, similar to cesarean delivery rates of other NIHF studies (69%-86%), 2,19,20 but higher than the cesarean delivery rate in the USA (32%).…”

“…8 Possible explanations include increased surveillance and advances in neonatal care. 8 Almost 75% of live births were cesarean deliveries, similar to cesarean delivery rates of other NIHF studies (69%-86%), 2,19,20 but higher than the cesarean delivery rate in the USA (32%). 21 The majority (63%) of primary cesarean deliveries in this cohort were performed for hydrops fetalis.…”

“…Mirror syndrome is another reported obstetric complication of hydrops fetalis, marked by generalized edema (62%), hypoalbuminemia (55%), hypertension (39%), and anemia (39%) 7 . Preterm birth and cesarean delivery also occur more often in NIHF pregnancies 2,8 . Additionally, pregnancies with hydrops fetalis experience higher rates of postpartum hemorrhage (PPH), blood transfusion, and polyhydramnios 6 …”