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Too Much Weight Gain During Pregnancy Increases Complication Risks

The National Institutes of Health
Spotlights (NIH)

August 29, 2013

A variety of factors can make it difficult for women to maintain a healthy weight during pregnancy. But recent NICHD supported research affirms the importance of not gaining too much weight during pregnancy to reduce the risk for complications.

New findings from an NICHD-supported study of more than 8,000 women nationwide found that first-time mothers who gained more weight than recommended were at increased risk for high blood pressure during pregnancy, cesarean delivery, and delivering a larger-than-gestational-age (LGA) infant.

These findings reaffirm the recommendations of the Institute of Medicine (IOM) regarding weight gain during pregnancy. Those recommendations, released in 2009, were based on research from the NICHD, other NIH Institutes, and the March of Dimes.

The IOM guidelines recommend the following:

  • Pregnant women who are underweight (body mass index [BMI] of less than 18.5) should gain 28 to 40 pounds
  • Pregnant women who are normal weight (BMI of 18.5 to 24.9) should gain between 25 and 35 pounds.
  • Pregnant women who are overweight (BMI of 25 to 29.9) should gain between 15 and 25 pounds.
  • Pregnant women who are obese (BMI greater than 30) should limit weight gain to between 11 to 20 pounds.

Research—including these recent findings—indicates that staying within the recommended levels can help lower the health risks for mothers and can lead to healthier outcomes for babies. Read more about the IOM recommendations at Weight Gain During Pregnancy: Reexamining the Guidelines. To learn more about the NICHD’s research on pregnancy and weight, including an interview with one of the authors, select a link below.

Evaluating the Data
Dr. Cathy Spong Discusses the Study
Other NICHD Research on Pregnancy and Weight
More Information

The newly released findings came from researchers in the Maternal-Fetal Medicine Units (MFMU) Network, which is supported through the NICHD’s Pregnancy and Perinatology Branch (PPB). Using data that had been collected previously for a Network preeclampsia prevention study, MFMU researchers evaluated pregnancy outcomes for more than 8,000 pregnancies, including first-time mothers. For this secondary analysis, the researchers looked at outcomes based on total weight gain above and below the 2009 IOM guidelines on weight gain during pregnancy.

Of the 8,293 pregnant women who participated in the study at multiple sites across the country:

  • 9.5% had weight gain below the recommended guidelines.
  • 17.5% remained within the weight gain guidelines.
  • 73% of women gained more weight than recommended.

Among women who gained more than the recommended amount, the researchers found an increased risk of gestational high blood pressure in all of the BMI categories; that is, even if a woman was underweight before pregnancy, she was still at increased risk for high blood pressure during pregnancy if she gained more than the recommended weight. High blood pressure during pregnancy can lead to preeclampsia, a life-threatening condition that can cause serious short- and long-term health problems for the mother and her fetus.

The study also found that women who were normal pre-pregnancy weight and those who were overweight were also at increased risk for cesarean delivery and for having an LGA infant. Previous research showed that LGA babies are at higher risk for birth injury and may have low blood sugar and other problems related to glucose regulation at birth.

Cathy Spong, M.D., the Associate Director of the NICHD Extramural Research Program and one of the authors of the study said that part of the problem may stem from the mistaken belief that a woman is “eating for two” during pregnancy. In fact, pregnant women should eat only around 300 additional calories per day during pregnancy.

Understanding the effects of weight gain before and during pregnancy is an important part of the NICHD’s research portfolio. For instance:

  • NICHD research has linked maternal obesity to birth defects such as neural tube defects, conditions in which the spinal cord, brain, and related structures do not form properly.
  • Other NICHD researchers also found that pre-pregnancy obesity increases the risk for an infant to be born with a heart defect by around 15%. Read more about these research findings at Risk of Newborn Heart Defects Increases with Maternal Obesity.
  • NICHD research also found that women who are overweight or obese spend more time in labor than do women who are normal weight.

These are just a few of the Institute’s ongoing projects related to weight gain, overweight, and obesity before and during pregnancy.

The knowledge gained from this and other research adds to the spectrum on evidence-based information on promoting healthy pregnancies. By understanding more about potential pregnancy complications, including those related to weight, researchers can help minimize risks and improve outcomes for mothers and their babies.

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