Interactive effect of maternal overweight/obesity during first trimester and elevated gestational blood glucose on macrosomia and large for gestational age birth

  Objective  To evaluate independent and joint effects of early pregnancy body mass index (BMI) and blood glucose level in the second trimester on the risk of macrosomia and large for gestational age (LGA) birth.

  Methods  We extracted records of 35 554 women with singleton pregnancy attending their first antenatal care visit before 13 gestational weeks in 7 urban districts of Tianjin city from 2009 through 2010 from Tianjin Maternal and Child Health Information System. The collected information of the women included demographics, general status of the pregnancy, BMI during the first trimester, and 50g oral glucose challenge test (GCT). Logistic regression analysis was adopted to assess independent and joint effect of overweight/obesity in first trimester and blood glucose level during second trimester on macrosomia and LGA birth.

  Results  The results of multivariate logistic regression analysis demonstrated that compared to those with the BMI of 18.5 – 23.9 kg/m^2, , the overweight and obese pregnant women were at higher risk of giving birth to macrosomic neonates (overweight: odds ratio OR = 1.886, 95% confidence interval 95% CI: 1.730 –2.057; obesity: OR = 3.724, 95% CI: 3.280 – 4.228) and LGA neonates (overweight: OR = 1.721, 95% CI: 1.606 – 1.845; obesity: OR = 3.230, 95% CI: 2.908 – 3.586); in comparison with those with the GCT of < 7.8 mmol/L, the pregnant women with the GCT of ≥ 7.8 mmol/L were more likely to give birth to macrosomic neonates (OR = 1.402, 95% CI: 1.287 – 1.529) and LGA neonates (OR = 1.342, 95% CI: 1.253 – 1.437). Compared to those with low BMI (< 24.0 kg/m²) and low GCT (< 7.8 mmol/L), the pregnant women only with elevated GCT had increased risks of giving birth to macrosomic neonates (OR = 1.392) and to LGA neonates (OR = 1.365); whereas the pregnant women with both elevated GCT and overweight/obesity were at much higher increased risks of giving birth to macrosomic neonates (OR = 3.438) and to LGA neonates (OR = 2.948), suggesting a significant additive interactive effect of overweight/obesity and elevated GCT (P < 0.05).

  Conclusion  Overweight/obesity during first trimester and elevated GCT during second trimester are independent risk factors for macrosomia and LGA birth among pregnant women and the effects of the two risk factors are interactive in an additive manner.