Significance of third trimester hba1c as a predictor of adverse obstetric outcome in diabetic mothers- a prospective observational study

Background: Diabetes is emerging as a new epidemic in today’s era with the increase in obesity and sedentary lifestyles, affecting a large proportion of the female population extending to reproductive age group. It is well known to have short and long term consequences for the fetus and mother. Thus, proper control of diabetes in pregnancy is essential to ensure better obstetric outcomes. Objective: The present study was undertaken to determine the significance of HbA1c levels in third trimester in predicting adverse maternal and fetal outcomes. Methods: It was a Prospective observational study of 100 pregnant women with diabetes who attended the antenatal clinic and delivered at St. Isabel’s hospital, Chennai from May 2017 to Oct. 2017. Pre-gestational diabetes was diagnosed according to ADA criteria and testing for GDM was done with 75g Oral Glucose Tolerance Test (OGTT) according to IADPSG criteria at the first visit and at 24 -28 weeks. Patients with diabetes were managed according to hyperglycemia control. Hba1c value in late third trimester or at time of delivery was noted and a value of < 6% was considered normal. Obstetrical and perinatal outcomes were noted and the data was compared using Chi-square test. Odds ratio and 95% confidence interval were used to compare association of HbA1c with various maternal and neonatal complications. Regression analysis was used to estimate the relationship among various categorical variables. Results: Fetomaternal outcomes were compared among patients with HBA1c ≥6% and <6%. Adverse maternal outcomes when HbA1c was ≥6% included hypertension (42% vs. 6%, p<0.001, OR=11.7) and preterm labour (35% vs. 14%, p=0.01, OR=3.24). Spontaneous onset of labour (19% vs. 42%) when HbA1c was ≥6% with greater percentage of vaginal deliveries when HbA1c <6% (80% vs 20%). Neonatal outcome analysis revealed higher birth weight (51% vs. 39%, p=0.013) and greater incidence of LGA (45% vs. 3%, p<0.001, OR=27.5) with HbA1c ≥6%. Adverse neonatal metabolic complications included hypoglycemia (39% vs. 7%, p=0.001, OR=8.08), hyperbilirubinemia (58% vs. 29%, p=0.006, OR=3.39) and hypocalcemia (16% vs. 3%, p=0.016, OR=6.44). Regression analysis of various maternal and neonatal complications showed highest relation of third trimester HbA1c with maternal hypertension (p=0.002) followed by LGA (p=0.01). Conclusion: HbA1c is a sensitive tool for prediction of foetomaternal complication in patients with diabetes and should be advised to ensure optimum outcomes when self monitoring of blood glucose is not feasible.