Fat Moms and Fat Babies? Weight Gain During Pregnancy

Heidi Mallis

December 2009

The obesity epidemic in the U.S. is affecting newborns and pregnant women. New guidelines for gaining weight during pregnancy aim to reverse the current trend, where women gain too much weight, causing health problems for the mother and her baby.

Twenty years after the previous guidelines were issued, the Institute of Medicine released updated guidelines in 2009 for weight gain during pregnancy.1 The report concluded that women today are heavier when they become pregnant than women used to be, and they gain more weight during their pregnancy than before. This can harm the health of both the mother and the baby.

What are the risks associated with being overweight or obese during pregnancy?

An obese woman is less likely to go into labor naturally (or even to have it induced successfully), which means she is much more likely to have a Caesarean section. Obesity during pregnancy also increases the risk of several birth defects, such as cleft palate, intestinal tract abnormalities, and heart defects.2

When a baby’s birth weight is greater than 10 pounds, known as macrosomia (which merely means heavy birth weight), the baby is likely to grow up to be an obese child. Obese children tend to remain obese during their teenage years and as adults.

A study conducted by researchers at Virginia Tech College of Veterinary Medicine showed that a diet high in saturated fat among pregnant mice was associated with the offspring developing chronic disease in adulthood. The adult offspring had signs of hyperglycemia (high levels of sugar in the blood), insulin resistance, obesity, and hypertension, despite being fed healthy rodent food.3 This finding is significant because it shows that a child’s healthy eating habits can’t necessarily make up for a mother’s poor eating habits during pregnancy.

There is also evidence that children may have a higher risk of developing asthma if their mothers are overweight when they get pregnant. Obesity increases the amount of cytokines (which are small proteins) circulating in the body that cause inflammation, which is a type of immune response. When a pregnant woman’s body is in a constant state of inflammation due to excess fat (as opposed to weight gain from the developing fetus), it affects the lung development of the baby in the womb and may lead to a higher risk of asthma symptoms in childhood.4

A study of pregnant women in the Netherlands found that women who had excessive weight gain during pregnancy were eating more, were not physically active, and also were not getting enough sleep.5 The relationship between too little sleep and obesity has been known for several years: people who do not get enough sleep tend to eat more, and people who are obese tend to have sleep apnea, resulting in less sleep.6

Many women find that their usual strategies for keeping their weight down don’t work during pregnancy. For example, when clothes get tight or the scale shows a few extra pounds, that is usually a reminder to watch what you eat; but those clues are not helpful for a women who is pregnant.

The following suggestions can help a woman stay healthy during pregnancy:

  • To figure out how much weight you should gain during pregnancy, first determine your pre-pregnancy Body Mass Index (BMI) using the Centers for Disease Control and Prevention (CDC) Web site7: http://www.cdc.gov/healthyweight/assessing/bmi/adult_bmi/english_bmi_calculator/bmi_calculator.html
  • Compare your BMI with the 2009 Institute of Medicine/National Research Council guidelines for weight gain during pregnancy1:
  • Pre-pregnancy BMI Total weight gain for one baby (lb.) Total weight gain for twins (lb.)
    Underweight: BMI less than 18.5 kg 28-40 No guideline available
    Normal weight: BMI between 18.5-24.9 kg 25-35 37-54
    Overweight: BMI between 25.0-29.9 kg 15-25 31-50
    Obese: BMI greater than 30.0 kg 11-20 25-42
  • Discuss these guidelines with a health care provider to create a personalized plan that best meets your pregnancy needs.
  • Maintain a healthy diet, emphasizing foods that are low in fat and high in fiber. In addition to prenatal vitamins, aim for foods that are a natural source of folic acid (also called folate), such as orange juice, green leafy vegetables, beans, peanuts, broccoli, asparagus, peas, and lentils. Folic acid can reduce the risk of birth defects of the brain and spine.8
  • Participate regularly in physical activity. The American College of Obstetricians and Gynecologists recommends a minimum of 30 minutes of moderate physical activity a day for pregnant women (unless there are medical or obstetric complications). Of course, avoid activities with a high risk of falling or abdominal harm.9

By maintaining a healthy weight, it is possible to reduce the risk of complications during pregnancy and delivery, and decrease the chances of your child developing health problems later on.


1. Institute of Medicine (2009, May). Weight gain during pregnancy: re-examining the guidelines. Retrieved from
http://www.iom.edu/~/media/Files/Report%20Files/2009/Weight-Gain-During-Pregnancy-Reexamining-the-Guidelines/Report%20Brief%20-%20Weight%20Gain%20During%20Pregnancy.ashx (Accessed November 30, 2009).

2. Rowlands I, Graves N, de Jersey S, McIntyre D, Callaway L (2009, October 12). Obesity in pregnancy: outcomes and economics. Seminars in fetal and neonatal medicine: 1744-65.

3. Liang C, Oest M, Prater M (2009, September 11). Intrauterine exposure to high saturated fat diet elevates risk of adult-onset chronic diseases in C57BL/6 mice. Birth Defects Res B Dev Reprod Toxicol. -Not available-, ahead of print.

4. Scholtens S, Wijga A, Brunekreef B, Kerkhof M, Postma S, Oldenwening M, de Jongste J, Smit H (2009, September 29). Maternal overweight before pregnancy and asthma in offspring followed for 8 years. International Journal of Obesity. -Not available-, ahead of print.

5. Althuizen E, van Poppel M, Seidell J, van Mechelen W (2009, September 29). Correlates of absolute and excessive weight gain during pregnancy. Journal of Women’s Health. -Not available-, ahead of print.

6. Patel SR, Hu FB (2008). Short sleep duration and weight gain: a systematic review. Obesity, March 2008; 16(3): 643-653.

7. Centers for Disease Control and Prevention (2008, April 27). Healthy Weight: Adult BMI Calculator. U.S. Department of Health and Human Services. Retrieved from http://www.cdc.gov/healthyweight/assessing/bmi/adult_bmi/english_bmi_calculator/bmi_calculator.html (Accessed October 19, 2009).

8. Centers for Disease Control and Prevention (2005, October 5). Having a healthy pregnancy. U.S. Department of Health and Human Services. Retrieved from http://www.cdc.gov/ncbddd/pregnancy_gateway/during.html (Accessed June 15, 2011).

9. American College of Obstetricians and Gynecologists (2002, January). ACOG Committee Opinion No. 267: Exercise during pregnancy and postpartum period. 99 (1): 1-3.