Maternal HbA1c levels in nondiabetics not tied to adverse pregnancy outcomes: IJOGR study
Pregnancy is a state where there are various physical, structural, hormonal and psychological adjustments in the maternal metabolism to adapt for the fetus. Normal pregnancy is observed as a diabetogenic state as there is a continuous rise in post-prandial blood sugars during the whole pregnancy and in late pregnancy there is increased insulin response.
There is energy stored in the early gestation which can be seen in the form of elevated maternal fat stores and reduction in concentration of free fatty acids. Maternal fasting glucose will progressively decrease as there is increase in fetoplacental utilization of glucose in later weeks of gestation. Also there is significantly lower insulin sensitivity during pregnancy when compared to that after delivery.
There are two forms of diabetes mellitus during pregnancy: pre-gestational or overt diabetes mellitus and gestational diabetes mellitus (GDM). Because of this poor glycaemic control preconceptionally in women with overt diabetes and who are more prone for diabetes during pregnancy, particularly during first trimester, the foetus is placed at a high risk of congenital anomalies especially cardiac and neural tube defects.
Glycated haemoglobin (HbA1c) is a formed by nonenzymatic linkage of haemoglobin with any sugar. When the blood sugar levels are increased, which is observed in case of diabetes, it is depicted by elevated levels of glycated haemoglobin in the plasma. This feature can be used as a criterion for the diagnosis of diabetes mellitus. HbA1c is a measure which ascertains the average plasma glycemic level for the preceding three months. Hence it can also be used as a test for monitoring and surveillance of glycemic control in the diabetics. Kanukolanu, Gopalan and Rajagopalan designed a study to determine the estimation of HbA1c and correlating its value with the maternal and foetal outcome.
The study was done among 60 healthy pregnant women who are between 18-35 years. HbA1c was estimated and they were followed up for assessing pregnancy outcome. Birth weight >90th percentile, primary C-section, neonatal hypoglycaemia, any NICU admissions and neonate's condition at discharge were assessed.
- The mean of haemoglobin, OGTT (fasting, 1-hour and 2-hours) and HbA1c were 11.25mg/dL, 81.73mg/dL, 120.75mg/dL, 104.13mg/dL and 5.24% respectively.
- The trimester specific HbA1c levels in the second and third trimesters in the present study were found to be 5.11% and 5.27% respectively.
- Among the study subjects 51 (85%) women had term delivery whereas 9 (15%) women had preterm delivery. 42 women (70%) had normal delivery, 1(1.7%) patient had operative vaginal and the remaining 17(28.3%) patients had emergency caesarean section.
- It was observed that 5(8.3%) subjects had LBW and 55(91.7%) had normal birth weight neonates. Two neonates among the study subjects had NICU admission for other reasons.
Complications during delivery and foetal complications showed no association with the HbA1c value. Authors found no association between body mass index(BMI) and HbA1c and foetal birth weight in different groups of women.
In present study authors did not include variables like macrosomia or preeclampsia but, HbA1c value ≥5.15% has sensitivity for predicting type of delivery (caesarean section), gestational age (preterm) and birth weight of baby (low birth weight) as 63%, 67% and 58% respectively whereas specificity of the same variables were found to be 59%, 47% and 60% respectively.
The authors concluded, "Our study showed no significant association between the maternal HbA1c levels in non diabetic mothers and the adverse pregnancy outcome. This shows that all the confounding factors and possible variables should be taken into consideration while estimating the HbA1c level and correlating its effect on maternal and foetal outcomes."
Source: Kanukolanu, Gopalan and Rajagopalan / Indian Journal of Obstetrics and Gynecology Research 2021;8(2):177–181;