Pregnancies in obese women are more difficult for mother and child than those in normal-weight women, says the director of maternal fetal medicine at Allegheny General Hospital.

There also is a higher risk of stillbirths and, indirectly, because of a greater risk of birth defects, diabetes and hypertension, for miscarriage, said Dr. Ronald Thomas.

"Obesity gives you a risk [for certain medical conditions] whether you're pregnant or not," Dr. Thomas said, "and the two most common medical conditions are diabetes and hypertension. And even if you don't come into pregnancy with either diabetes or hypertension, the stress of pregnancy may bring out gestational diabetes or gestational hypertension.

Hypertension is one of the symptoms of preeclampsia, which Dr. Scott Kauma, reproductive endocrinologist and director of the Jones Institute for Reproductive Medicine at West Penn Allegheny Health System, said is yet another condition overweight pregnant women experience in higher numbers. "... Blood pressure goes up and they start peeing out a lot of protein and it often necessitates delivery."

"The other issue, of course," Dr. Thomas said, "is when time comes for delivery it turns out there's a higher risk for delivering by cesarean section."

That's because overweight women tend to have bigger-than-normal babies who won't fit through the birth canal. "Then on top of that you add the fact that surgery of any sort is riskier if you're overweight," Dr. Thomas said.

Babies don't get off easy, either. They are at risk for both gestational diabetes and being overweight that can haunt them through their entire lives.

"For babies there's an indirect issue," Dr. Thomas said. "If you are overweight even if you don't have diabetes you're at risk for having a baby that is overweight. The problem is if you are a baby born with increased adipose cells that baby is at risk for being an overweight adult.

"So what we're talking about is the potential for a mother to give her baby a lifelong medical issue because if mom is obese and has diabetes the baby has an increased chance of being obese and the same risk for a medical problem as any obese adult."

A report in the Journal of the American Medical Association said that there is an increased but small risk that babies born to obese women may have certain birth defects such as spina bifida and neural tube defects.

"That's correct," Dr. Thomas said, "but on the other hand there are decreased risks for some birth defects such as gastroschisis, abdominal wall defects, which is one of the things that surprised me. ...

"It all comes down to relative risk, not absolute risk," he added. "If your risk is four times the baseline rate, but the baseline risk is 1 percent, your relative risk is 4 percent ... so chances are you won't have a problem.

"A four-fold risk is significant, but you have to put it in perspective."

Dr. Thomas said the risk that stirs the biggest response is the chance that an obese mother is going to give birth to an overweight baby who becomes an overweight adult.

"Oddly that seems to be the thing that moms respond to," he said.

All of those risks, of course, could be diminished if the mothers lost weight through bariatric surgery, the most effective weight-loss tool.

"They clearly have safer pregnancies and so if you look at the same patient and compare pregnancies from when they were obese and when they are of normal weight, the pregnancy with the normal-weight mom is clearly safer."