It used to be that pregnant women were told they should gain no more than about 25 pounds, no matter what their current weight. Anything more and your doctor scolded you, threatened you or even prescribed diet pills (aka amphetamines). Eventually doctors worried that newborns were too small. Guidelines changed to allow pregnant women to gain more weight.

Today, we face:

  • Widespread obesity
  • Unrestrained pregnancy weight gain
  • Giant-sized babies
  • Widespread diabetes
  • More premature babies born than ever before
  • Ever-increasing C-sections
  • More mothers and unborn babies dying during pregnancy

Given the state of the nation's waistline, it's time for a serious look at weight gain and pregnancy.

Beyond baby fat

Tina was 25 years old during her first pregnancy. Her body mass index (BMI) indicated that, at 29 percent, she was just under obese. She didn't exercise and gave herself permission to enjoy eating for two. As her weight went up, her doctor warned she was at risk for high blood pressure, diabetes and having a C-section, but Tina wasn't worried: She was healthy, young and could lose the weight later.

By the time her daughter was born, Tina had gained 70 pounds. She had a hard time delivering her baby because her birth canal was blocked by fat. Her 10-pound daughter was born by C-section. Because her infant was very large, she had trouble breathing and keeping her blood sugar steady. She spent several days in the neonatal intensive care unit with IVs and oxygen, instead of in her mother's arms. Today, she's an overweight toddler.

With her next pregnancy, Tina carried 50 extra pounds, gained another 60 and developed gestational diabetes. Seven daily needle-pokes (four to check blood sugar and three for insulin) gave Tina a health wake-up call. She was 27 and 100 pounds overweight. She knew she and her kids faced a future filled with needles and illness unless she changed everything.

Tipping the scales

Dr. Desiree Bley, an obstetrician/gynecologist at Women's Health Today in Portland, Oregon, says: "About half my patients start their pregnancies already obese. This is a huge change from what physicians saw 20 years ago. Women don't talk to their doctors about their weight before they get pregnant. They talk about infertility and then realize there's a direct connection. Being overweight changes the way we use estrogen to produce and release healthy eggs."

In the 1980s and '90s, two things started the widespread problem of too much weight gain during pregnancy.

  1. The Health and Medicine Division (HMD), a division of the National Academies of Sciences, Engineering, and Medicine (formerly the Institute of Medicine), announced guidelines for pregnancy weight gain that were less strict.
  2. High-fructose corn syrup, processed foods and super-sized portions became common in the American diet.

"Women becoming pregnant now grew up with an extra layer of fat and are used to unhealthy eating habits," says Dr. Bley. "Pregnancy is physically challenging enough without obesity."

Too much body fat changes pregnancy. It:

  • Changes how and what hormones your body produces
  • Changes how blood sugar is used in your body and the way it moves through the placenta to your baby
  • Makes your heart work harder
  • Damages many organ systems of your body

The result is you are more likely to have diabetes, heart problems or high blood pressure. You are less likely to be able to deliver your baby vaginally. Your baby may grow too big because it gets too much blood sugar. Or, your baby may be born prematurely or too small because you had problems with blood circulation.

Guidelines for good health

The IOM current guidelines for safe, healthy weight gain in pregnancy (for single babies) depend on how heavy the mother is. They are:

  • Obese (BMI over 30): 11–20 pounds
  • Overweight (BMI 25.0 to 29.9): 15–26 pounds
  • Normal weight (BMI 18.5 to 24.9): 25–35 pounds
  • Underweight (BMI below 18.5): 28–40 pounds

Sticking to these guidelines isn't easy. According to Dr. Bley: "Eating for two is a myth. Pregnant women only need 300 extra calories per day. That's an orange, an egg and two extra cups of milk. Pregnancy only adds 23 pounds. That's baby, placenta, extra blood, tissue and fluid. Everything else is you."

Exercise is key for controlling your weight, improving circulation and improving how your blood sugar is absorbed. How should you start? First, get the green light from your doctor. Then start with low-impact aerobics, gentle stretching and strength training. Up to 60 minutes of daily walking or swimming is safe during most pregnancies. "Keep it low-impact," Dr. Bley says. "Falling down is bad in pregnancy."

According to RandiJo Taurel, yoga instructor at The Shop, in Park City, Utah, yoga and pregnancy are a natural fit. "Prenatal yoga is an easy way to start exercising, no matter what shape you're in. You can practice on your own or in class. The moves are simple and offer immediate benefits."

Change is possible

During her second pregnancy, Tina learned healthy eating from a nutritionist, began walking and added yoga. After her baby was born, she followed that with mother–baby fitness classes. Within a year, she'd shed 60 pounds. She enrolled her children in swimming lessons and changed her family's diet. By changing her habits, Tina turned a wake-up call during an unhealthy pregnancy into a lifetime of health habits for herself and her family.

Published on Aug. 16, 2010; updated on May 12, 2014.