Effects of gestational weight gain and
HbA1C
on fetal growth and birthweight in women with obesity
Maja Lecic Bonnichsen, Elisabeth Qvigstad, Lill Trine Nyfløt, Guttorm Haugen, William R. P. Denault, Marie Cecilie Roland Abstract
Introduction
Fetal growth and birthweight are influenced by various endogenous and exogenous factors during pregnancy. Pregnant women with obesity face higher rates of complications, which can impact fetal growth. This study aims to explore how gestational weight gain and metabolic factors, such as HbA1C and adipokines, are associated with fetal growth in the second and third trimesters and with birthweight in Norwegian women with a pregestational BMI ≥35 kg/m 2 .
Material and Methods
We conducted a prospective longitudinal cohort study at the Department of Gynecology and Obstetrics at Drammen Hospital from 2016 to 2019. We included 163 pregnant women (nulliparous 47.6%) with pregestational BMI ≥35 kg/m 2 and singleton pregnancy, excluding type 1 and 2 diabetes. Gestational weight gain (GWG) was calculated as the difference between pregestational weight and the last weight before delivery. Fetal growth was monitored via ultrasonography at five time points, alongside fasting metabolic samples withdrawn around 18 and 36 weeks' gestation. Statistical analyses were conducted using linear regression in Stata Version 17.0.
Results
Mean birthweight was within normal ranges (mean z ‐score 0.117). However, the proportions of LGA (18.4%) and SGA (12.9%) were high. One in three women was diagnosed with GDM, of whom approximately one in three needed medical treatment. In the adjusted multivariate analyses, only HbA1C measured around gestational week 36 and the weekly weight gain remained positively associated with birthweight, biparietal diameter, and mean abdominal diameter.
Conclusions
In this population of pregnant women with pBMI ≥35 kg/m 2 , weekly GWG calculated from weight measurement around 36 weeks' gestation was positively associated with birthweight ( z ‐score), mean abdominal diameter (MAD), and biparietal diameter (BPD). HbA1C was positively associated with birthweight ( z ‐score). Our results indicate that HbA1C and the modifiable GWG are exposures with the potential to influence fetal growth and birthweight. Nevertheless, current follow‐up protocols do not routinely emphasize these factors. Their evaluation therefore warrants further investigation.