Science by press release

Every few months brings another news story telling fat pregnant women that they need to lose weight so they don’t contribute to the ‘obesity epidemic’ or have fat babies. With so many press releases coming out all saying the same thing — especially when they come from the same sources and quote the very same researchers — women and their loved ones need to know that they’re seeing marketing, not science.

Basing any health decision on media marketing can not only put a mother’s health and welfare in jeopardy, but her baby’s, too.

Unconscionably, a lot of health scares target pregnant women and new mothers because it’s the most anxious time in their lives. Pregnant women are understandably worried for their health and that of the new life in their care. Special interests take advantage of this vulnerability to promote diets, supplements, tests and all manner of products and services promising health and well being.

“The increased awareness for well-being in pregnancy provides a strong impetus for lifestyle changes,” wrote Dr. Raul Artal, M.D. in Expecting Fitness. “It is well recognized that 40 percent of all medical conditions in our urbanized society are behavior related, that is, they arise because of sedentary lifestyle and poor nutritional habits that result in obesity, cardiovascular disease, diabetes, and hypertension. Pregnancy provides a unique opportunity for behavioral modification.”

Besides the fallacies in these assertions and the lack of evidence that pregnancy weight gain is to blame for the obesity epidemic, most people would argue that the focus of every pregnant woman and her doctor shouldn’t be on her figure, but on what is best for her and her baby. We’ve covered several times just why the weight gain guidelines are as they are, and that recommendations to restrict pregnancy weight gain has been tried before. Medical professionals quickly found that advice for weight gain restrictions endangered babies, and babies were having poorer chances for survival and more health problems. Medical guidelines were reversed to what we have today and the research continues to show that these recommendations help to ensure a safe pregnancy, optimal fetal growth and healthy babies. Without working from good information, we could repeat history.

But, as we learned in August from a St. Louis University media release, there is a movement afoot to revise the pregnancy weight gain guidelines downward to address the ‘obesity epidemic’ and a Robert Wood Johnson Foundation-commissioned review is coming up this fall.

Today’s media has been filled with stories of a new study by Dr. Artal and colleagues at St. Louis University School of Medicine, purportedly showing that fat pregnant women should lose weight to avoid pregnancy complications and avoid having a fat baby. “Obese women don’t have to gain any weight during their pregnancy,” he said in the press release. “Pregnancy is a big factor in this [obesity] epidemic.” If this sounds familiar, it should. We heard about a study claiming to find the same thing on June 5th. It also came from a St. Louis University press release with the same quotes from Dr. Artal.

The June study, published in Applied Physiology, Nutrition and Metabolism, however provided no evidence for making such sweeping public health recommendations. It was a small study comparing 39 pregnant women with gestational diabetes who were put on special diet and exercise program to 57 pregnant gestational diabetics enrolled in a diet group. While these women were closely followed and most didn’t gain weight during pregnancy, the researchers weren’t looking at underweight babies nor the effects their recommendations could have on pregnancies among the general population.

Which brings us to today’s press release and news of the study published in the current issue of Obstetrics & Gynecology. “The findings are significant in addressing a major public health crisis .... This study confirms what we’ve suspected all along — that obese women don’t have to gain any weight during their pregnancy,” Dr. Artal said.

But it didn’t.

This was not an interventional trial to examine if controlling weight gain improved pregnancy outcomes, it was an observational study looking for correlations among a database of ‘obese’ pregnant women in Missouri who delivered term babies (37 or more weeks gestation) from 1990 to 2001. Premature births, multiples (twins, triplets, etc.) and stillbirths were excluded from their analysis. They used the Missouri linked birth-death certificate registry to determine pregnancy outcomes and identify pregnancy-associated hypertenion and cesarean deliveries. Prepregnancy BMIs were calculated from self-reported prepregnancy weight and height recorded on the birth certificates. Pregnancy weight gain was abstracted from the women’s medical charts and the obstetric records.

You can already see lots of problems here. The women who were heaviest, for instance, were also more likely to be poorer, minority women and most likely to delay seeking prenatal care. As the March of Dimes explains, for instance, pregnant women facing very stressful situations, such as low socioeconomic status, long working hours, strenuous or stressful work, long commutes to work or unemployment, have higher rates of preeclampsia. So, not surprisingly, slightly higher preeclampsia rates were also correlated with the heavier women in this cohort. Another important note is that the heaviest women in this study population were also older and higher maternal age is also associated with higher rates of gestational diabetes and preeclampsia. Good prenatal care can effectively care for these conditions to ensure safe pregnancies and healthy babies.

But the one thing medicine alone can’t overcome is undernutrition and the resulting fetal growth retardation and underweight babies. The most concerning results of this study was the direct correlation between increasing pregnancy weight gain and reductions in small-for-gestational age babies. Among the Class I obese women, for example, gaining 35 pounds or more had rates of underweight babies of 5%, versus 10% among those gaining less that 15 pounds. That’s a doubling of the risk for underweight babies by recommending lower weight gains for ‘obese’ women.

This study didn’t even examine the effects of such recommendations on women of ‘normal’ weight status. But another study in the same issue of Obstetrics & Gynecology did. Researchers at Saint Louis University, Department of Obstetrics and Gynecology in Missouri, led by Dr. Thomas D. Myles, M.D., examined the same Missouri birth certificate data from 1999 to 2001 for 94,696 women with ‘normal’ prepregnancy BMIs. They found that women who gained less than 25 pounds during pregnancy had less preeclampsia, but a 114% increased risk for small-for-gestation babies. In contrast, women who gained more than 35 pounds cut the risk for small babies by more than half. In balancing the risks and benefits, while they couldn’t bring themselves to recommend 35-pound weight gains, the researchers concluded that adhering to the current weight gain guidelines “results in lower risks for adverse pregnancy, labor, and delivery outcomes when comparing all outcomes collectively.”

According to the latest (May 2, 2007) CDC National Vital Statistics Report, there were 333,427 low birth weight babies born in the United States in 2004. Population-wide recommendations to restrict pregnancy weight gain, risking doubling these numbers, could have devastating effects. As the CDC report states:

Birthweight and period of gestation are the two most important predictors of an infant’s subsequent health and survival. Infants born too small and/or too soon have a much greater risk of death and both short-term and long-term disability than those born at term or with birthweights of 2,500 grams or more. Because of their much greater risk of death, infants born at the lowest birthweights and gestational ages have a large impact on overall U.S. infant mortality.

There is no evidence for serious concern about babies with healthy baby fat, but there is considerable evidence of concern for those without enough. As reviewed previously, “low birth-weight babies may be associated with ... heart problems, lung problems, digestive problems, sometimes even into learning disabilities later on in life,” said Paul Hasselback, senior medical health officer with Interior Health of British Columbia. In fact, low birth weight babies are more likely to have long-term disability or die during their first year of life than larger babies. They’re also more apt to need specialized care in a neonatal intensive care unit, according to the March of Dimes, which explains these small babies encounter more medical issues from respiratory and heart problems, bleeding in the brain, intestinal and vision problems.

While Dr. Artal and colleagues concluded that “limited or no weight gain in obese pregnant women has favorable pregnancy outcomes.” It is doubtful that women, knowing the facts, would agree.

To protect themselves, women need to recognize that news comes from press releases and the media mindlessly reports these marketing pieces and turns up the obesity panic dial. Media is not the source for credible, evidence-based information upon which to make any dietary or health decisions.

Babies born to mothers of all sizes deserve to enjoy a healthy start from mothers eating well. Mothers and babies deserve public health guidelines based on the very best and most careful, sound and objective medical evidence. The welfare of children and improving their chances for healthy futures should be the concern, not whether they or their mums are fat.

© 2007 Sandy Szwarc