Junkfood Science: Priority: healthy children

April 06, 2007

Priority: healthy children

As a neonatal intensive care nurse for many years, the media’s spin of a study released this week left me shuddering with worry for the well being of pregnant women and their babies. It exemplified the problem of reporters having insufficient expertise in the field they are reporting on. Or, maybe it just highlighted how our society’s obsession over obesity and fitness has caused everyone to lose all ability to think.

The suggestion widely splashed across news headlines was that gaining even the recommended number of pounds during pregnancy was harmful and leading to childhood obesity. This will understandably influence some women to try to restrict their pregnancy weight gain — and put the health of themselves and their babies in jeopardy.

Not only did the media draw conclusions far beyond what this study could credibly support, it failed to give consumers the full story. Virtually every media outlet in the country repeated the Associated Press story: “Even accepted weight gains in moms-to-be can lead to fat toddlers, study says.”

The standard advice for how much weight a woman should gain during pregnancy may need to change, according to a rigorous and provocative study suggesting that even accepted weight gains may raise the risk of having an overweight toddler.

Women in the study who gained the recommended amount of weight ran four times the risk of having a child who was overweight at age 3, compared to women who gained less than the advised amount. The outcome was about the same for women who gained more than the advisable amount....

The advice and spin on television wasn’t much better. Even Dr. Nancy Snyderman suggested to NBC Today Show viewers that the pregnancy weight guidelines needed to be changed and advised women to watch their weight while they are pregnant to help prevent childhood obesity. While NBC’s Today Show offers a running stream of poor science surrounding food and health, this isn’t the first time NBC’s chief medical editor has overstated the evidence in her reports. Doctors in growing numbers are concerned about the nonevidence-based medical advice being given on NBC, as Dr. Kevin Pho, M.D., wrote on Monday. Of course, the problem isn’t exclusive to NBC. Next Wednesday, for instance, Dr. Snyderman is hosting a segment on what is needed to “help kids avoid the lifelong health trap that is obesity” as part of PBS’s special “Fat: What no one is telling you.” As Junkfood Science readers learned in February, this is the program underwritten by GlaxoSmithKline, as part of its guerilla marketing campaign.

A close look at this study

Let’s consider a few important aspects of this week’s study, published in the current issue of the American Journal of Obstetrics and Gynecology, that weren’t reported in the news.

This was an observational study looking for correlations by dredging through data collected in Project Viva. The results of their computer modeling were reported as odds ratios. Already, we’ve been given the information we need to take its findings with special caution and recognize that any correlations they derive won’t tell us anything about causation.

For this database, 2,128 women had been signed up between April 22, 1999 and July 31, 2002 from eight obstetric offices with Harvard Vanguard Medical Associates in the Boston, MA area. Only women with singleton pregnancies who received prenatal care within the first 22 weeks of gestation, continued their care at the Harvard centers, and wrote English were eligible. The women in Project Vera were generally well-educated women with health insurance. But the group included in this week’s study was even more restrictive than the original cohort. Half of the original population of women in Project Viva were not included. Those lost in followup were two times more likely to be Black or unmarried and 50% more likely to be Hispanic. The women studied differed considerably from the general population, meaning findings among them cannot be generalized to all women.

And what did this study find about the 3-year olds? The actual data shows that among the toddlers with “normal” body mass indexes, about half of their mothers had gained more weight during their pregnancies than recommended by the Institutes of Medicine. Of the toddlers who were “overweight,” about half of their mothers had gained “excess” weight, too (a difference of less than a quarter of a pound). Among the very fattest toddlers, just over half of the mothers had gained excess weight. And just under half of the mothers of underweight/low weight toddlers had gained “excess” weight.

Are you getting the idea? Gaining “excess” amounts of weight made little difference. There was a mean difference in pregnancy weight gain among all of the mothers of a mere 3 pounds. Any clinically meaningful conclusions drawn from a nominal 3-pound difference are questionable...especially, since the study provided no information on the health of the toddlers. There was no evidence to support insinuations that the larger children were somehow worse off.

While the researchers were focused on the women who had gained excess weight during their pregnancies, similar attention wasn’t given to the more critical issue of the women who failed to gain the amount of weight considered necessary to ensure healthy fetal development. In this study, 22% of the babies who were small for gestational age had mothers who had gained inadequate weight, as recommended by the IOM. Their data showed that the risks for having a baby with intrauterine growth retardation was two times higher among women not gaining adequate weight. This concurs with the body of research for nearly the past century.

It is important to understand why adequate pregnancy weight gain is such a concern among healthcare professionals and the evidence and history behind the development of current recommendations. Gaining adequate weight and eating well during pregnancy have proven vital for ensuring the healthy growth and development of the baby and a safe pregnancy. During the 1940s and 1950s, it became standard practice in the United States to restrict weight gain during pregnancy to less than 20 pounds. The fears were that gaining more could risk toxemia and birth complications believed to be associated with larger babies. By the 1960s, however, public health officials recognized this advice was putting babies at risk and found that among mothers following these weight gain restrictions, their babies had poorer chances for survival. The Food and Nutrition Board’s Committee on Maternal Nutrition reviewed the problems, practices and research between nutrition and pregnancy outcomes and its 1970 report suggested more weight was needed to achieve optimal fetal growth. Women who are underweight have the greatest risks for having babies who suffer from intrauterine growth retardation and even back then the evidence suggested that they needed to gain more during their pregnancies. Since that report, countless studies have shown desirable weight gain and adequate food helps ensure a safe pregnancy and healthy baby. The Institutes of Medicine again reviewed the research and evidence and today’s guidelines are the results of their 1990 report, Nutrition During Pregnancy: Part I: Weight Gain.

Already, there are growing concerns among healthcare professionals with today’s obsessions with thinness among women of childbearing and the added risks it brings to pregnancies. A paper just published in the February issue of the American Journal of Clinical Nutrition, reported that “maternal thinness is a strong predictor of both preterm birth and fetal growth restriction.”

Rising economic standards and better nutritional status of mothers have played significant roles in the “unparalleled drop in infant mortality seen since 1900,” according to the CDC. “From 1915 through 1997, the infant mortality rate declined greater than 90%...and from 1900 through 1997 maternal mortality rate declined almost 99%.”

Researchers in a recent issue of the Journal of the American Society for Nutritional Sciences reported that despite advances in prenatal care, about 5% of American babies still suffer from intrauterine growth retardation (IUGR) and that mother’s nutrition plays a critical role in helping to ensure optimal fetal development. As Michael S. Kramer, M.D., professor of Pediatrics and of Epidemiology and Biostatistics at Montreal Children’s Hospital, Quebec, has noted, much of IUGR is the result of a low prepregnancy weight and low weight gain during pregnancy “due to low energy intake. No important contribution has been established for micronutrient intake, nor have different fetal growth trajectories been demonstrated to reflect the timing of exposure to nutritional or other etiologic factors.” In other words, calories appear important, and today’s popular obsessive focus on avoiding “fattening” foods may be ill-founded. Conversely, he’s noted, as birthweights have increased there have been reductions in stillbirths and fewer neural tube defects. Undernutrition, it appears, is the much greater issue — that is, if we’re concerned about the health of a baby or child.

It is probably common sense to most readers that a baby not growing normally during pregnancy is at risk, but few may be aware just how staggering the risks are for IUGR babies just for surviving infancy. According to a recent paper in Current Opinions in Obstetrics and Gynecology, IUGR is responsible for about 50% of normal-formed stillbirths and babies weighing less than 5 1/2 pounds** at birth have mortality rates 5 to 30 times higher than average birth weights. Babies under 3 1/3 pounds have mortality rates 70 to 100 times greater. Babies suffering from undernutrition during pregnancy are also at increased risk for neurological, respiratory, intestinal and circulatory problems during the neonatal period.

Although improvements in medical care have been the main force in overall declines in infant mortality seen in our country over recent years, there remains a persistent discrepancy among various racial/ethnic groups. Specifically, Black babies more than twice as likely to die as white infants. The IOM report found that the lag appears most related to a disproportionate number of Black babies underweight. Dr. Kramer also noted the evidence shows that disparities in infant mortality are primarily due to IUGR, rather than preterm births, but that more is needed to fully understand the causes and effectively prevent adverse pregnancy outcomes.

But few of us realize the long-term affects of IUGR. In contrast to media-filled concerns over baby fat, the evidence on the life-long ramifications for children who suffer IUGR far exceeds anything suggesting harm from having a toddler who crosses the arbitrary cut-off for “overweight.”

According to Dr. Kramer, IUGR not only increases morbidity and mortality during infancy, but deficits persist into adulthood. “Neurological, cognitive and behavioral deficits appear to be most marked from the pre-school years through adolescence,” he said. “A number of epidemiological studies have shown associations between low birth weight and earlier and higher prevalence of hypertension, coronary heart disease, adult onset diabetes, chronic respiratory disease, autoimmune thyroid disease and some forms of cancer.” His research has noted the importance of early detection of IUGR, just as we do for babies and young children who are failing to thrive and falling off their growth curves.

The rest of the story

Which brings me to another key finding in this week’s study that received absolutely no notice. While all of the focus was on the 9% of toddlers considered “overweight,” the 31% of children who were underweight or low-weight were not even mentioned!

The researchers even left off their final statistical adjusted odds calculations any information on these children. Furthermore, the data was reported in an odd way — using unique cutoff percentiles and curiously not giving the standard breakdowns to enable the numbers of "underweight" toddlers to be precisely identified. Only 5% of the children as newborns were considered small for their gestational age, while nearly a third of them at 3 years of age were low or underweight. This would suggest that significant numbers of growing children might be falling off their growth curves.

The underweight/low weight toddlers also had 3 times greater percentage of mothers who’d gained inadequate weight during their pregnancies. It is disconcerting that the researchers neglected to flesh this out to determine if these were women over-reacting to weight concerns and not only undereating themselves, but underfeeding their children in an effort to keep them from getting fat. Or, the mothers could be in hardship situations that might be putting the health of their children at risk. However, given this cohort was primarily upper-class white women in the Boston area, it is probably more likely to be the former. This very serious possibility is made even more so by the fact this study will likely accentuate weight concerns among many new mothers.

Why might these researchers have chosen to focus on the 9% of toddlers labeled “overweight” and not the 31% underweight/low weight? The clue might be found in an important detail the media left out of the news this week. This study was conducted by researchers at the Dept. of Ambulatory Care and Obesity Prevention Program, which has as its stated mission “to lessen the burden of obesity-related disorders by conducting epidemiologic, health services and intervention research studies.”

While many of the babies in the ICU are there for reasons not known or anything the mother did wrong, I’ve watched too many tiny babies suffer, too many endure tragic outcomes, too many babies die, and too many lives of young mothers devastated by grief and regret because they had been afraid to eat and gain weight during their pregnancies. I only hope young women will follow the advice of their own doctors and not what they hear in the media.

© 2007 Sandy Szwarc

[Photo: SA Premies]

** While low birthweight has become a popular and easily-accessible marker for risks among specific populations, researchers, such as Dr. Allen Wilcox at the National Institute of Environmental Health Sciences, are increasingly arguing that the evidence indicates it isn’t low birthweight itself that causes risk. -- Just as weight at any age isn’t what’s important. This is a topic for another time, but brings home the point that our focus should be on the health of a child, not his/her weight.

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