If you're overweight and expecting, you face increased health risks, but you can turn things around. Here's how to have a healthy pregnancy.

Sharon Biddinger, 24, now pregnant with her second child, was almost 50 pounds heavier going into this pregnancy than she was the first time around. She attributes the weight gain after her first child to a lack of exercise and eating whatever she wanted.

The extra weight really took a toll on Sharon emotionally. She would often inspire insensitive comments like, "When are you going to lose that baby weight?" "It was a horrible and depressing time," she says.

Sharon has since come to terms with the emotional side effects of her weight gain and the fact that her larger size has very real medical implications. At 198 pounds and 5 feet, 3 inches, Sharon is clinically obese. That diagnosis means this pregnancy carries a lot more risk than her first one.

RELATED: The Dangers of Excessive Weight Gain During Pregnancy

A Growing Problem

You might think a diagnosis of obesity is reserved only for extreme cases. But according to the most recent National Health and Nutrition Examination Survey, 3 of 10 women are clinically obese, meaning they have a body mass index (BMI) of 30 or above. BMI, which is a measure of your weight in comparison to your height, is the tool doctors use to identify obesity. Sadly, the percentage of women entering pregnancy obese parallels the national statistic.

But while most women are keyed in to the emotional and aesthetic aspects of being plus-size and pregnant, few really understand the medical reality of obesity. "

You can be shapely and healthy, but it is not possible to be obese and healthy," says Laura Riley, MD, medical director of labor and delivery at Massachusetts General Hospital, in Boston. "We are talking about a medical disorder that has major implications for 1) your pregnancy, 2) your fetus, and 3) your life," she says.

Risks of Being Overweight and Pregnant

According to the American College of Obstetricians and Gynecologists, during pregnancy, obese women have a higher risk for miscarriage, preeclampsia, gestational diabetes, and hypertension.

As a result, many also are more likely to need a cesarean delivery. When you have gestational diabetes, you are more likely to have a larger baby.

"There is definitely an epidemic of babies getting bigger, and bigger babies mean more c-sections. It carries down," says Jacques Moritz, MD, director of gynecology at St. Luke's-Roosevelt Hospital Center, in New York City. Hypertension and preeclampsia also increase the chance of cesarean section. If the mother's blood pressure rises during delivery, she could suffer a stroke, and the baby could be deprived of his blood supply. To prevent these consequences, the doctor has no choice but to perform a cesarean, says Dr. Moritz.

Cesarean surgery also can be more complicated for an obese woman. Extra fat under the skin makes it more difficult to find the right placement for spinal anesthesia and harder to find a vein for an intravenous line, says Naomi Torgerson, MD, assistant chief of obstetrics and gynecology at Kaiser Permanente, in Richmond, California. It also is harder to transfer a heavy patient if she needs to be moved, a real problem in an emergency.

There also are serious risks to the babies, including a greater chance of neural tube defects, stillbirth, large-for-gestational-age, and higher rates of childhood obesity. The higher rate of neural tube defects may be due to poor nutrition, says Dr. Moritz. It is possible to be overweight and undernourished if you eat a lot of empty calories. And, he says, bigger babies are more likely to be stillborn.

If you are overweight or obese and have been making half-hearted attempts to change your habits, this may be just the motivation you need. "Pregnancy is the perfect time to make an effort," says Dr. Riley. "Many women have their child's best interests at heart."

With time, Sharon's desire to be there for her children ultimately motivated her to change her habits. "I'm now more active, I'm eating right, and my blood pressure is stable," she says. "I try to take care of myself, not for the vanity of it but because I am not doing right by my son if I can't push him on the swing without running out of breath."

Medical complications also can give you the insight you need to change. Gestational diabetes gives you a taste of what it is like to live every day as a diabetic -- constantly monitoring your blood sugar and facing a multitude of possible medical problems. After dealing with that, you may be ready to do whatever you can to avoid diabetes. Dr. Torgerson has seen many patients inspired this way. "It's a wake-up call that gives women the opportunity to change things," she says.

What You Can Do to Lose Weight

If you're thinking about making a change, start small by taking sensible steps toward habits that will lead to gradual weight loss.

Start with your diet.

Eat more vegetables, fruits, whole grains, lean meats, and low-fat dairy products. Cut out sugary soft drinks and fried foods. Try eating several small meals throughout the day rather than one or two large meals, and forget about eating for two. After all, you need no extra calories in your first trimester and only about 300 additional daily calories in your second and third trimesters — about the number of calories in a yogurt and a banana.

Get active.

This is perhaps most important. One of the best things you can do is to start walking regularly. Walking 20 to 30 minutes a day is something you can do safely throughout your pregnancy, says Dr. Riley. In pregnancy, the goal, according to the Institute of Medicine's guidelines, is to gain 25 to 35 pounds if you are normal weight, 15 to 25 pounds if you are overweight, and 15 pounds if you are obese.

RELATED: 5 Simple Pregnancy Exercises for Every Trimester

In Dr. Torgerson's experience, "any gain over 25 pounds is the amount you need to work off through diet and exercise over the next year or so. But a lot of women don't do that." Her advice: Ideally, you should gain the appropriate amount of weight during pregnancy and make every effort to lose any extra before you get pregnant again.

A Weighty Subject

You might be surprised to know that many doctors feel uncomfortable bringing up the issue of weight. They're concerned you might feel judged, says Dr. Riley, and choose another practitioner. But she stresses how important it is for patients and doctors to communicate about this topic: "Obesity is a touchy subject, but this is not about looking good or bad. This is about health," she says.