medwireNews: Mothers who gain weight between their first and second pregnancies have a higher risk for gestational diabetes than those who maintain a stable weight, an analysis of the Medical Birth Registry of Norway suggests.
As reported in PLOS Medicine, the 3814 women whose body mass index (BMI) increased between 1 and 2 kg/m2 between pregnancies were twice as likely to develop gestational diabetes as the 11,512 with a stable BMI (<1 kg/m2 difference) between pregnancies, with a relative risk (RR) of 2.0 after adjustment for factors including maternal age, smoking, and interpregnancy interval.
And compared with those who maintained a stable weight, the 3279 participants whose BMI increased between 2 and 4 kg/m2 had a 2.6-fold increased risk for gestational diabetes, while the 1517 with a BMI increase of more than 4 kg/m2 were more than 5 times as likely to develop the condition (adjusted RR=5.4).
“Pregnant women who increase their weight by ≥1 BMI unit from their first to second pregnancy should be closely monitored during their second pregnancy to reveal development of [gestational diabetes], irrespective of prepregnant BMI,” say Linn Sorbye (University of Bergen, Norway) and study co-authors.
Indeed, in stratified analyses, interpregnancy weight gain was significantly associated with gestational diabetes risk both for women who had a normal weight (BMI<25 kg/m2) and those who were overweight (BMI≥25 kg/m2) at the time of their first pregnancy. However, the association was stronger for those with a BMI of less than 25 kg/m2.
“Normal-weight women generally have a higher insulin sensitivity than overweight and obese women,” explain the authors, and suggest that “an additive effect of the physiological decrease in insulin sensitivity during pregnancy may overload the capacity and increase the susceptibility to develop [gestational diabetes], especially in normal-weight women who are used to higher insulin sensitivity.”
The team also found that overweight women whose BMI decreased at least 2 kg/m2 between their first and second pregnancy had a lower risk for gestational diabetes than those whose BMI remained stable, but the difference did not reach statistical significance.
Sorbye and colleagues caution that their study was not able to account for potentially confounding factors such as family history of gestational diabetes and vigorous exercise, and that self-reported height and weight measurements “might cause bias due to misclassification.”
Nevertheless, they conclude: “Our results support a metabolic mechanism behind the increased risk of [gestational diabetes], represented by the weight change itself.”
And they recommend that “[e]fforts to promote healthy weight in the reproductive population need to expand their focus to include healthy maternal weight from preconception throughout reproduction.”
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