Isolated polyhydramnios in the third trimester or polyhydramnios secondary to late-onset gestational diabetes: is it worth distinguishing?

OBJECTIVE: The aim of this study was to compare pregnancy outcomes of patients with polyhydramnios due to late-onset gestational diabetes mellitus and patients with isolated polyhydramnios. METHODS: Of the women who fully participated in prenatal examinations at Etlik Lady Z & uuml;beyde Hospital between January 1, 2018, and December 31, 2019, women with polyhydramnios of nonfetal-placental origin manifesting in the third trimester were retrospectively reviewed. Women with normal 75-g oral glucose tolerance test results between 24 and 28 weeks gestation who met the inclusion criteria were enrolled in the study and divided into two groups based on the results of rescreening with the 75-g oral glucose tolerance test for polyhydramnios in the third trimester: women with isolated polyhydramnios (group 1) and women with late-onset polyhydramnios due to gestational diabetes mellitus (group 2). RESULTS: There were a total of 295 participants, of whom 35 (11.8%) were diagnosed with polyhydramnios due to late-onset gestational diabetes mellitus. There were no differences in the main outcomes. Birthweight and gestational age at birth were identified as independent risk factors for predicting composite maternal outcome {[odds ratio (OR)=1.273, 95% confidence interval (CI) 1.063-1.524, p=0.009]} and composite neonatal outcome (OR=0.606, CI 0.494-0.744, p<0.001), respectively. CONCLUSION: Polyhydramnios in late pregnancy without evidence of pregnancy-related causes leading to polyhydramnios may be a sign of late-onset gestational diabetes mellitus in women with a normal prior oral glucose tolerance test. As pregnancy outcomes and management were indifferent, it does not seem necessary or useful to diagnose whether or not late-onset gestational diabetes mellitus is present.