A large-scale Korean study published in the Diabetes and Metabolism Journal has found that women who gain weight in the years up to pregnancy have an enhanced likelihood of developing gestational diabetes mellitus (GDM), even if they are not obese.

Researchers analyzed the data from the Korean National Health Insurance Service database from nearly 160,000 women who gave birth between 2015 and 2017 and had participated in two national health screenings, i.e., one three years before and one year before their estimated conception date. Based on changes in body weight over those two years, women were divided into five groups i.e., from significant weight loss to significant weight gain.

Of the 146,363 women included in the final analysis, about 7.5% developed GDM. The study found a clear dose-response relationship. Women who gained between 5% and 10% of their pre-pregnancy weight had a 12% increased risk of GDM, while those who gained 10% or more faced a 34% higher risk. This association was more pronounced in women who were not obese or did not have metabolic syndrome.