Small-for-gestational age placentas associate with an increased risk of adverse outcomes in pregnancies complicated by either type I or type II pre-gestational diabetes mellitus

Introduction: One-fifth of pregnancies with pre-gestational diabetes mellitus (pre-DM) yield placentas <10th percentile small for gestational age (SGA), compared to a non-diabetic population. We hypothesized that SGA placentas of women with pre-DM, whether type I (T1DM) or type II (T2DM), exhibit distinct histopathological changes and pregnancy outcomes compared to pre-DM pregnancies with an AGA placenta. Methods: We conducted a retrospective, cohort study of placentas from pregnant women enrolled in the Diabetes in Pregnancy Program at Brown University between 2003 and 2011, by comparing pre-DM patients with SGA placentas to pre-DM patients with AGA placental weights. Results: The SGA placenta groups were associated with an increased risk for adverse clinical outcomes, compared to AGA placentas in pregnancies complicated by either T1DM or T2DM. Compared to their AGA pre-DM counterparts, T1DM, SGA placentas show increased peri-villous fibrin/fibrinoid deposition, thrombosis in fetal blood vessels, and meconium staining. Moreover, the histopathology of SGA placentas from T2DM is characterized by decidual vasculopathy, accelerated villous maturity, and erythroblastosis, compared to T2DM AGA placentas. The contrasting placental pathologies between the two pre-DM SGA phenotypes evolved independent of patient demographics and were unrelated to indicators of the glycemic control present at early gestational ages. Discussion: A sub-population of pre-DM women with either T1DM or T2DM diabetes that have an SGA placenta are at increased risk for adverse clinical outcomes in pregnancy, compared to pre-DM women with AGA placental weights.