Idiopathic polyhydramnios and postnatal outcomes of children: The role of exome sequencing

ObjectivesThe objective of our study was to evaluate the long-term outcome of children born from a pregnancy complicated by idiopathic polyhydramnios. The secondary objective was to investigate factors associated with adverse outcomes.MethodsWe conducted a retrospective study in two prenatal diagnosis centers between January 1, 2009 and December 31, 2020. Inclusion criteria were pregnancies with a diagnosis of idiopathic polyhydramnios, defined by a deepest pocket greater than 8 cm, no detectable abnormality at ultrasound and a negative amniotic fluid assessment including karyotype, chromosomal microarray, biochemical assays (electrolytes and digestive enzymes), and viruses (parvovirus B19 and cytomegalovirus). One-year outcomes of these children were collected. The primary endpoint was adverse postnatal outcome, defined by at least one of the following criteria: stillbirth, neonatal death, or serious and incurable condition diagnosed in the first year of life.ResultsOf the 245 women referred for isolated polyhydramnios, 73 were diagnosed with idiopathic polyhydramnios after prenatal investigations. The mean age at follow-up of children was 28 months (95% CI 20-36). An adverse outcome occurred in 25% of cases (18/73), with one stillbirth, two neonatal deaths, and 15 severe conditions diagnosed postnatally, including a rate of monogenic disorders of 8.2% (6/73). Pediatric follow-up was normal for 75% of the children (55/73), including a rate of 9% (5/55) of curable conditions. Repeated amnioreduction was independently associated with an adverse outcome.ConclusionPregnant women with polyhydramnios should be informed of the increased risk of 25% of perinatal mortality and serious conditions diagnosed after birth. What's already known about this topic?Few retrospective studies have assessed long-term outcomes and have reported an increased risk of postnatal diagnosis of anomalies in the first years of life in the range of 9%-28%.What does this study add?Idiopathic polyhydramnios, defined by the absence of etiology after prenatal investigations, is associated with a 25% risk of adverse outcomes, including a 21% rate of serious and incurable conditions diagnosed postnatally. When idiopathic polyhydramnios is diagnosed, it may be relevant to consider trio exome sequencing plus consultation with a geneticist in order to increase the diagnostic yield.