Correlation of placental pathology and perinatal outcomes with Hemoglobin A1c in early pregnancy in gravidas with pregestational diabetes mellitus

Introduction Data on the correlation among Hemoglobin A1c (HbA1c), placental pathology, and perinatal outcome in the pregestational diabetic population is severely lacking. We believe that this knowledge will enhance the management of pregnancies complicated by pregestational diabetes. We hypothesize that placental pathology correlates with glycemic control at an early gestational age. Methods This is a retrospective cohort study conducted from 2003 to 2011 at a large tertiary care center. Women included had a singleton gestation, preexisting diabetes mellitus, and information about delivery and placental pathology available for review. Placental pathology and perinatal outcomes were compared across three groups of patients with differing HbA1c levels (<6.5%, 6.5–8.4%, and ≥8.5%). Results 293 placentas were examined. HbA1c was measured at a mean of 9.5week gestation. Median HbA1c was 7.5%, interquartile range 6.5%–8.9%. 23% of the cohort had HbA1c <6.5%, 41.9% between 6.5% and 8.4%, and 34.8% > 8.5%. BMI varied significantly by group (35.4 vs. 34.4 vs. 32.0 respectively, P = 0.04). Individual placental lesions did not vary with HbA1c levels. The incidence of acute chorioamnionitis differed significantly in the type 1 population and “distal villous hypoplasia” varied in the type 2 population. Discussion The results show that HbA1c values in early pregnancy are poor predictors of future placental pathologies. As a result, HbA1c values obtained during early gestation (which reflect the level of glycemic control over an extended period of time) do not correlate with any particular placental pathology, despite reflecting the potential for placental insults secondary to pre-gestational diabetes.