Glycosylated hemoglobin level in the second trimester predicts birth weight and amniotic fluid volume in non-diabetic pregnancies with abnormal screening test.

OBJECTIVE

To investigate relationship between glycemic control in first half of pregnancy by measuring mid-pregnancy HbA1c and neonatal birth weight and amniotic fluid volume.

METHODS

We prospectively enrolled 220 pregnant women who received oral glucose tolerance test (OGTT) after positive gestational diabetes mellitus screening. We included 102 women with normal OGTT results into final analysis. We measured birth weight and amniotic fluid index (AFI) at 32-34 weeks.

RESULTS

Mean birth weight was 3313±426 g, and 15.7% of neonates were classified as large-for-gestational age (LGA). Mean Hb1Ac was 4.96±0.28%. Median AFI was 145 mm, and polyhydramnios rate was 2.9%. Birth weight was positively correlated with HbA1c level (r=0.373, p<0.001) and pre-pregnancy body mass index (BMI; r=0.351, p<0.001). Linear regression analysis showed that HbA1c and pre-pregnancy BMI were positive independent determinants of neonatal birth weight, and HbA1c was positive independent determinant of AFI. Receiver operating characteristics curve identified HbA1c level of 4.99 as optimal threshold for prediction of LGA with 93.8% sensitivity, 61.6% specificity and positive likelihood ratio (+LR) of 2.45 and pre-pregnancy BMI value of 25.2 as optimal threshold for prediction of LGA with 81.3% sensitivity, 57% specificity and +LR of 1.9.

CONCLUSION

In non-diabetic pregnant women with abnormal screening test, mid-pregnancy HbA1c level and pre-pregnancy BMI may predict neonatal birth weight. AFI in 32-34 weeks of gestation is related with mid-pregnancy HbA1c level.