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Health Officials Issue Revised Pregnancy Weight-Gain Guidelines For Obese Women

The Institute of Medicine and the National Research Council on Thursday issued revised U.S. weight-gain guidelines for obese pregnant women, in response to rising levels of obesity in the country and growing evidence that weight gain can cause health problems for women and their infants, the New York Times reports. The revision, which is the first since 1990, recommends that obese women -- those with a body mass index of 30 or more -- limit their weight gain to 11 to 20 pounds over nine months. The 1990 pregnancy guidelines did not specifically address weight gain for obese women, telling them instead to follow the recommendations for overweight women. According to health officials, the changes to the recommendations for obese women were required to keep up with the changing weight patterns among women in the U.S. The New York Times reports that about 27% of women of childbearing age are considered obese, while 55% fall into the categories of overweight or obese.The recommendations for women with BMIs of less than 30 did not change. They call for overweight women -- those with a BMI of 25 to 29.9 -- to gain 15 to 25 pounds over nine months, while underweight women -- with BMIs of less than 18.5 -- should gain 28 to 40 pounds, and normal-weight women -- with BMIs of 18.6 to 24.9 -- should gain 25 to 35 pounds (Parker-Pope, New York Times, 5/29).Time reports that pregnant women who do not gain enough weight face a higher risk of stunted fetal growth and preterm delivery. However, it is more common for women to gain too much weight, placing them at higher risk for conditions like gestational diabetes and high blood pressure. In addition, their infants are at increased risk of being born earlier, larger and by cesarean section. Time reports that excessive weight gain can increase a woman"s risk of postpartum obesity and elevate risks of heart disease and stroke because most women do not lose extra pounds gained during pregnancy. Many studies also have suggested that a woman"s gestational weight can predict potential weight problems in her offspring (Kingsbury, Time, 5/28).The committee that developed and issued the revision said that the existing guidelines were essentially on target but that women and their physicians need to work harder to help women reach a normal weight before pregnancy and avoid gaining too much weight during pregnancy, according to the Los Angeles Times (Roan, Los Angeles Times, 5/29). The guidelines also recommend more nutrition and exercise counseling during pregnancy, advising physicians or midwives to consult dieticians to shape a woman"s care regardless of her initial weight, the AP/Yahoo! News reports (Neergaard, AP/Yahoo! News, 5/28). The Los Angeles Times reports that health care professionals are expected to recognize and implement some of the recommendations; however, it is not mandatory to do so.Several experts on maternal obesity and child health expressed disappointment with the guidelines, arguing that obese women should gain little to no weight during pregnancy, according to the Los Angeles Times. They also argue the new guidelines do not do enough to address obesity before pregnancy. Maxine Hayes, state health officer for the Washington State Department of Health, said, "If we wait for every woman to be advised about weight gain after they become pregnant, it"s too late. It puts women and their babies on a trajectory that is unhealthy" (Los Angeles Times, 5/29).
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How Microbial Neighbors Settle Differences

Even microbes are governed by the principle of supply and demand - at least at the genetic level. Not all of their gene products, the blueprints for proteins, are required at all times. That means most of their genes only become active when they are needed, as is the case in higher organisms. In the simplest case, a transcription factor will activate the gene in question at the right time. Genes that are regulated in a somewhat more complex manner, on the other hand, are kept inactive by a repressor that is removed only when the gene is needed. Which of these two regulation mechanisms will develop is a question of demand, along the lines of a "use-it-or-lose-it" principle: if genes are frequently active, then, as a rule, they will be directly induced. Genes that encode more rarely used proteins, on the other hand, tend to be kept inactive by repressors. LMU physicist Ulrich Gerland and Professor Terence Hwa of the University of California have now demonstrated using computer simulations and theoretical analyses that another - indeed opposing - principle also comes into play: "wear-and-tear". According to this principle, direct activation can lead to harmful changes. "Which of the two principles prevails depends on evolutionary criteria such as the population size and the periods over which environmental changes take place," says Gerland. "Our study may serve as a useful basis for more detailed studies of the evolution of regulatory systems." (PNAS Early Edition, 22 Mai 2009)