medwireNews: Giving pregnant obese women metformin in addition to dietary and lifestyle advice does not reduce the likelihood of them having a baby with a high birthweight, show the results of the GRoW randomized trial.
This was despite metformin use resulting in less gestational weight gain, report Jodie Dodd (University of Adelaide and Women’s & Children’s Hospital, South Australia) and co-investigators.
“The use of metformin in this clinical setting should not be advocated,” they write in The Lancet Diabetes & Endocrinology. “Future research strategies should focus on improving women's health and diet to encourage weight loss before conception.”
A total of 524 women recruited from three hospitals at a median gestational age of 16.3 weeks were randomly assigned to take metformin up to a maximum of 2000 mg/day or placebo. In addition, they all received dietary and lifestyle advice, including two face-to-face sessions with a dietitian, one with a research assistant, and three telephone calls from the research assistant.
Medication allocation did not influence the likelihood of women giving birth to an infant weighing more than 4000 g, with this occurring in 16% of those in the metformin group and in 14% of those in the placebo group.
And there were no differences for any other infant outcomes, which included average birthweight, the proportion of babies that were large or small for gestational age, admission to the neonatal intensive care unit, and the presence of hypoglycemia that required treatment.
Among the women, average total gestational weight gain was numerically less in those who took metformin versus those who took placebo, at 7.48 versus 8.72 kg, but this was not statistically significant after accounting for variables including BMI category and socioeconomic status.
However, average weekly gestational weight gain was significantly lower in the metformin versus placebo group, at 0.38 versus 0.47 kg, and a significantly greater proportion of women remained below the maximum recommended weight gain, at 39% versus 27%.
In a linked commentary, Patrick Catalano (Tufts University School of Medicine, Boston, Massachusetts, USA) outlines the physiologic changes during pregnancy that may explain why interventions such as metformin treatment and targeted weight loss have had limited or no benefits.
“Newer strategies for limiting excessive gestational weight gain, based on maternal physiological changes in pregnancy complicated by obesity, need to be investigated,” he writes.
Catalano agrees with the researchers’ suggestion that reduction of excess weight before pregnancy might be a beneficial tactic. He concedes this would be challenging and “would require a concerted public health effort from the entire community” but notes that a “5–7% decrease in weight often results in improved metabolic conditioning” and would therefore be a “much better outcome than the frustration of not achieving an ideal weight.”
He concludes: “Such an approach might be the first step in breaking the vicious cycle of maternal obesity begetting obesity in the offspring.”
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