Combined associations of gestational diabetes mellitus and hypertensive disorders of pregnancy with placental complications and postpartum hemorrhage: a risk stratification analysis of a large retrospective cohort

Hypertensive disorders of pregnancy (HDP) and gestational diabetes mellitus (GDM) have each been independently associated with adverse obstetric outcomes; however, their combined associations with placental complications and postpartum hemorrhage (PPH) remain incompletely understood. The aim of this study was to examine the independent and combined associations of GDM and HDP with placental complications and PPH. Retrospective cohort study was conducted using data collected at a tertiary obstetric referral center during the 2023–2024 period among 7168 singleton deliveries. The study population was divided into 4 groups based on the presence of HDP and/or GDM. Multivariate logistic regression models and interaction testing were utilized to estimate the independent and combined associations of GDM and HDP with placental complications and PPH. A stepwise increase in adverse outcomes was observed across the exposure groups. Women with GDM alone had higher adjusted odds of placental complications (aOR 1.63) and PPH (aOR 1.35). However, the associations were stronger among women with HDP (placental complications aOR 3.31; PPH aOR 3.25). The highest adjusted odds were observed among women with concurrent GDM and HDP (placental complications aOR 5.44; PPH aOR 6.18). Moreover, multiplicative interaction analysis demonstrated statistically significant interactions between GDM and HDP for placental complications ( β = − 1.40, P = 0.032) and PPH ( β = − 1.60, P = 0.008), indicating that the combined association differed significantly from the individual associations on the multiplicative scale. Neonatal outcomes were also significantly worse in the GDM + HDP group, with a NICU admission rate of 32.6%. GDM and HDP were independently associated with placental complications and PPH, with the highest adjusted odds observed among women with concurrent GDM and HDP. These findings support clinical risk stratification of pregnancies complicated by both conditions; however, prospective multicenter studies incorporating detailed measures of disease severity and clinical management are needed to confirm these findings.