Isolated oligohydramnios in previous pregnancy is a risk factor for a placental related disorder in subsequent delivery

BACKGROUND: We aimed to assess the association between isolated oligohydramnios in previous pregnancy and the incidence of placental related complications in subsequent pregnancy. METHODS: This was a retrospective cohort study of live singleton births from a single university affiliated medical center during an eleven-year period of women with two subsequent deliveries at our center. An analysis of outcomes was performed for all second deliveries, comparing women for whom their first delivery was complicated by isolated oligohydramnios (previous oligohydramnios group), and women without isolated oligohydramnios in their first delivery (control group). Patients for whom their first delivery was complicated by small for gestational age, pregnancy induced hypertension and preterm birth were excluded. The study groups were compared for obstetric and early neonatal outcomes, recurrence of oligohydramnios and a composite of placental related pregnancy complications. RESULTS: A total of 213 in the previous oligohydramnios group and 5348 in the control group were compared. No differences were found between the groups in maternal age, body mass index, smoking and comorbidities. Gestational age at delivery was, 39.6 ± 1.3 vs. 39.3 ± 1.4 weeks, p = 0.006, in the previous oligohydramnios and controls respectively, although preterm birth rate was similar between the groups. The previous oligohydramnios group had a significantly higher incidence of oligohydramnios in second delivery, aOR 3.37, 95%CI 1.89–6.00, small for gestational age neonates, aOR 1.94, 95% CI 1.16–3.25, and overall placental related disorders of pregnancy, aOR 2.13, 95%CI 1.35–3.35. CONCLUSION: Pregnancies complicated by isolated oligohydramnios are associated with an increased risk of placental related disorders in subsequent pregnancy. Isolated oligohydramnios may be the first sign of placental insufficiency and an independent manifestation of the placental related complications spectrum.