Truths and myths about pregnancy & obesity.

Vitamins, weight gain, preterm birth and more

Ironically, despite excessive caloric intake, many obese women are deficient in vitamins vital to a healthy pregnancy. This and other startling statistics abound when obesityand pregnancy collide. Together, they present a unique set of challenges that women and their doctors must tackle in order to achieve the best possible outcome for mom and baby.

In the December issue of the journal Seminars in Perinatology, maternal fetal medicine expert Loralei L. Thornburg, M.D., reviews many of the pregnancy-related changes and obstacles obese women may face before giving birth. The following myths and truths highlight some expected and some surprising issues to take into account before, during and after pregnancy.

"I treat obese patients all the time, and while everything may not go exactly as they'd planned, they can have healthy pregnancies," said Thornburg, who specializes in the care of high-risk pregnancies and conducts research on obesity and pregnancy. "While you can have a successful pregnancy at any size, women need to understand the challenges that their weight will create and be a partner in their own care; they need to talk with their doctors about the best way to optimize their health and the health of their baby."

Myth or Truth?

Many obese women are vitamin deficient.

True

Forty percent are deficient in iron, 24 percent in folic acid and 4 percent in B12. This is a concern because certain vitamins, like folic acid, are very important before conception, lowering the risk of cardiac problems and spinal defects in newborns. Other vitamins, such as calcium and iron, are needed throughout pregnancy to help babies grow.

Thornburg says vitamin deficiency has to do with the quality of the diet, not the quantity. Obese women tend to stray away from fortified cereals, fruits and vegetables, and eat more processed foods that are high in calories but low in nutritional value.

"Just like everybody else, women considering pregnancy or currently pregnant should get a healthy mix of fruits and vegetables, lean proteins and good qualitycarbohydrates. Unfortunately, these are not the foods people lean towards when they overeat," noted Thornburg. "Women also need to be sure they are taking vitamins containing folic acid before and during pregnancy."

Obese patients need to gain at least 15 pounds during pregnancy.

Myth

In 2009, the Institute of Medicine revised its recommendations for gestational weight gain for obese women from "at least 15 pounds" to "11-20 pounds." According to past research, obese women with excessive weight gain during pregnancy have a very high risk of complications, including indicated preterm birth, cesarean delivery, failed labor induction, large-for-gestational-age infants and infants with low blood sugar.

If a woman starts her pregnancy overweight or obese, not gaining a lot of weight can actually improve the likelihood of a healthy pregnancy, Thornburg points out. Talking with your doctor about appropriate weight gain for your pregnancy is key, she says.

The risk of spontaneous preterm birth is higher in obese than non-obese women.

Myth

Obese women have a greater likelihood of indicated preterm birth - early delivery for a medical reason, such as maternal diabetes or high blood pressure. But, paradoxically, the risk of spontaneous preterm birth - when a woman goes into labor for an unknown reason - is actually 20 percent lower in obese than non-obese women. There is no established explanation for why this is the case, but Thornburg says current thinking suggests that this is probably related to hormone changes in obese women that may decrease the risk of spontaneous preterm birth.