Gaining Weight between Pregnancies Boosts Diabetes Risk

A new study suggests that women who gain weight between two pregnancies have a higher risk of developing gestational diabetes mellitus (GDM).

Researchers at the University of Bergen (Norway) conducted an observational cohort study that included 24,198 mothers and data on their two first pregnancies from the Medical Birth Registry of Norway (2006–2014). Weight change, defined as pre-pregnant body mass index (BMI) in the second pregnancy minus pre-pregnant BMI in first pregnancy, was divided into six categories. Relative risk (RR) estimates were then calculated for maternal age at second delivery, country of birth, education, smoking in pregnancy, inter-pregnancy interval, and year of second birth.

The results revealed that compared to women with stable BMI, women who gained weight between the pregnancies had higher risk of GDM. The RR for women gaining 1 to 2 BMI units was 2.0; for women gaining 2 to 4 units, RR rose to 2.6, and for women who gained over 4 BMI units, RR climbed to 5.4. RR increased significantly for women with BMI both below and above 25 at first pregnancy, although it increased more for the former group. The study was published on August 1, 2017, in PLOS Medicine.

“Women who were overweight at first pregnancy had the highest risk of GDM. However, the strongest risk associated with weight gain between pregnancies was found in women with BMI less than 25 in first pregnancy,” said lead author Linn Marie Sørbye, MSc, of the Department of Global Public Health and Primary Care. “Surprisingly, we found a preventive effect of GDM in overweight women who reduced their BMI more than two units from first to second pregnancy.”

GDM is defined as any degree of glucose intolerance with onset or first recognition during pregnancy. The definition applies whether insulin or only diet modification is used for treatment, and whether or not the condition persists after pregnancy. It does not exclude the possibility that unrecognized glucose intolerance may have antedated or begun concomitantly with the pregnancy. Approximately 7% of all pregnancies are complicated by GDM, with a prevalence of 1-14% that depends on the population studied and the diagnostic tests employed.

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