The risk of developing gestational diabetes mellitus (GDM) increases with increased weight gain between pregnancies, according to a study by Linn Sorbye of the University of Bergen, Norway, and colleagues.
GDM is defined as glucose intolerance of various degrees that is first detected during pregnancy. Both pre-pregnant body mass index (BMI) and gestational weight gain are known risk factors for GDM, which can cause health problems for both mothers and babies. In the new study, researchers used data from the Medical Birth Registry of Norway on 24,198 mothers with a first and second pregnancy between 2006 and 2014. The data included BMI at the start of each pregnancy as well as any diagnosis of GDM.
The overall absolute risk of GDM in second pregnancy was 18.1 per 1000 pregnancies. 35.6 % of women in the study gained more than 1 BMI unit (kg/m2) of weight between the start of their first pregnancy and the start of their second pregnancy. These women had an increased risk of developing GDM in their second pregnancy compared to women whose weight was stable (-1 to < 1 BMI units). Women who gained between 1 and 2 BMI units had a doubled risk (adjusted risk ratio (aRR) 2.0, 95% confidence interval (CI): 1.5-2.7), women gaining between 2 and 4 units had a 2.6 times increased risk (a RR 2.6, 95%CI: 2.0-3.5), and women gaining ≥4 BMI units had a five-fold increased risk (a RR 5.4, 95% CI: 4.0-7.4). These increased risks were strongest in women who had a BMI below 25 kg/m2 in their first pregnancy. Evidence of a preventive effect on GDM was seen in overweight women (BMI ≥25) who reduced their weight by ≥ 2 BMI units between pregnancies.
“Antenatal guidelines for monitoring GDM in pregnancy should add inter-pregnancy weight change as an independent risk factor for GDM with a routine stress-test of glucose tolerance during pregnancy in women with weight gain more than 1 BMI unit,” the authors say.
Abstract
Background: Being overweight is an important risk factor for Gestational Diabetes Mellitus (GDM), but the underlying mechanisms are not understood. Weight change between pregnancies has been suggested to be an independent mechanism behind GDM. We assessed the risk for GDM in second pregnancy by change in Body Mass Index (BMI) from first to second pregnancy and whether BMI and gestational weight gain modified the risk.
Methods and findings: In this observational cohort, we included 24,198 mothers and their 2 first pregnancies in data from the Medical Birth Registry of Norway (2006–2014). Weight change, defined as prepregnant BMI in second pregnancy minus prepregnant BMI in first pregnancy, was divided into 6 categories by units BMI (kilo/square meter). Relative risk (RR) estimates were obtained by general linear models for the binary family and adjusted for maternal age at second delivery, country of birth, education, smoking in pregnancy, interpregnancy interval, and year of second birth. Analyses were stratified by BMI (first pregnancy) and gestational weight gain (second pregnancy). Compared to women with stable BMI (−1 to 1), women who gained weight between pregnancies had higher risk of GDM—gaining 1 to 2 units: adjusted RR 2.0 (95% CI 1.5 to 2.7), 2 to 4 units: RR 2.6 (2.0 to 3.5), and ≥4 units: RR 5.4 (4.0 to 7.4). Risk increased significantly both for women with BMI below and above 25 at first pregnancy, although it increased more for the former group. A limitation in our study was the limited data on BMI in 2 pregnancies.
Conclusions: The risk of GDM increased with increasing weight gain from first to second pregnancy, and more strongly among women with BMI < 25 in first pregnancy. Our results suggest weight change as a metabolic mechanism behind the increased risk of GDM, thus weight change should be acknowledged as an independent factor for screening GDM in clinical guidelines. Promoting healthy weight from preconception through the postpartum period should be a target.
Authors
LM Sorbye, R Skjaerven, K Klungsoyr, NH Morken
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