Oligohydramnios: how severe is severe?

To investigate whether the severity of isolated oligohydramnios at term is associated with increased rates of adverse perinatal outcome.

A retrospective study conducted in a single medical center from 2017 to 2019. All low-risk pregnancies with incidental isolated oligohydramnios at term were included. The degree of oligohydramnios was arbitrarily classified into mild (AFI = 41-50 mm), moderate (AFI = 21-40 mm) and severe (AFI = 0-20 mm).

A total of 610 women were included: 202 with a mild (33.1%), 287 moderate (47.0%), and 121 severe oligohydramnios (19.8%). Non-reassuring monitor requiring immediate delivery and worse composite neonatal outcome were more common among severe than mild or moderate oligohydramnios (14.0% and 6.4%, 7.3% respectively; p = .039 and 19.8%, 10.9% and 11.8%, respectively; p = .048).

Low-risk pregnancies with isolated severe oligohydramnios at term have a higher tendency toward non-reassuring fetal monitoring requiring prompt delivery and adverse neonatal outcomes, this calls for close intrapartum surveillance.