Maximum Vertical Pocket Versus Amniotic Fluid Index: Assessing Adverse Pregnancy Outcomes in Patients With Polyhydramnios

ABSTRACT Objectives To describe differences in outcomes in pregnancies complicated by polyhydramnios based on whether the diagnosis was made by maximum vertical pocket (MVP), amniotic fluid index (AFI) or both. Methods This was a retrospective cohort study examining ultrasound assessment of amniotic fluid in singleton pregnancies, June 2014 to May 2021, with amniotic fluid volume measured at ≥ 20 weeks gestation. The proportion of pregnancies with mild, moderate or severe polyhydramnios diagnosed by (1) MVP, (2) AFI and (3) both MVP and AFI was evaluated. Modified Poisson regression models estimated the relative risk of adverse outcomes for pregnancies with polyhydramnios compared to those with normal fluid. All models were adjusted for potential confounders and analyses stratified by the presence or absence of foetal anomalies. Results Of 14 883 pregnancies, 13 557 (91.1%) had both normal AFI and MVP. Polyhydramnios was most frequently diagnosed by MVP ( n = 602/1326, 45.5%). All cases diagnosed by either MVP or AFI were mild. Those with polyhydramnios by both MVP and AFI had an increased risk of perinatal mortality (adjusted relative risk [aRR] = 5.94, 95% confidence interval [95% CI] 3.07−11.50), including IUFD (aRR = 5.58, 95% CI 2.81−11.09) and neonatal death (aRR = 13.07, 95% CI 1.72−99.60). Findings were similar when the analysis was stratified by the presence or absence of foetal anomalies. Conclusions The use of MVP was associated with a higher likelihood of polyhydramnios diagnosis versus AFI. Polyhydramnios, diagnosed by either MVP or AFI, was mild. Polyhydramnios diagnosed by both measures was associated with an increased risk of perinatal mortality.