Metformin May Reduce Weight Gain, Preeclampsia

The oral medicine metformin is the most commonly prescribed diabetes drug in the world, with more than 61 million prescriptions filled in 2012 in the United States alone. And according to new research out of King’s Hospital in London, although the medicine does not appear to reduce the risk of having a large baby for obese women, it may help reduce weight gain during pregnancy and cut the risk of a dangerous condition known as preeclampsia.


Metformin works by decreasing the amount of glucose made by the liver and by improving insulin sensitivity in the liver, muscle, and fat cells. Because of this effect on insulin sensitivity and previous research indicating that metformin can reduce weight gain[1] in pregnant women with gestational diabetes, the investigators theorized that the medicine might lower the odds of having a large newborn in obese women (a body-mass index[2] of 35 or more) without diabetes, who are at higher risk of having large babies. About one in three women[3] in the United States is obese.

To test this hypothesis, the researchers randomly assigned obese women in the 12th through 18th week of pregnancy to take either 3.0 grams of metformin or a placebo (inactive treatment) daily until delivery. A total of 202 participants received metformin and 198 received placebo.

The researchers found that the medicine did not reduce the odds of the women having a large baby, with nearly 17% of those receiving metformin having a “large for gestational age” baby (a birth weight in at least the 90th percentile), compared to 15% of those receiving placebo. However, the medicine was found to decrease weight gain during pregnancy by an average of nearly 4 pounds, and those taking metformin also had a substantially lower risk of preeclampsia, with 3% of the metformin users developing the condition compared to 11% of the placebo users. Preeclampsia[4] is a serious pregnancy complication defined by high blood pressure and signs of damage to organ systems such as the kidneys. Left untreated, the condition can be fatal for mother and baby.

“Preeclampsia is one of the important pregnancy complications that we’ve been trying to reduce for decades, with variable success,” noted study author Hassan Shehata, MD.

The researchers note that the study did not have enough participants to definitively prove that metformin cuts preeclampsia risk, and they hope to conduct a future study to address that question.

For more information, see the article “Diabetes Drug May Not Help Obese Women Have Normal-Weight Babies”[5] or the study’s abstract[6] in The New England Journal of Medicine. And to learn more about metformin, see “Metformin: The Unauthorized Biography”[7] by diabetes educator Wil Dubois, BS, AAS, CPT, TPT.

If you live in the area of Anchorage, Alaska, you’ll want to check out the upcoming “Taking Control of Your Diabetes” Health Fair. Bookmark[8] and tune in tomorrow to learn more.

  1. metformin can reduce weight gain:
  2. body-mass index:
  3. one in three women:
  4. Preeclampsia:
  5. “Diabetes Drug May Not Help Obese Women Have Normal-Weight Babies”:
  6. study’s abstract:
  7. “Metformin: The Unauthorized Biography”:

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Diane Fennell: Diane Fennell has been an editor at Diabetes Self-Management magazine since 2003. She is currently the Editorial Director. (Diane Fennell is not a medical professional.)

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