Sitting down to a meal can be daunting for an expectant mother weighing conflicting recommendations about which foods are good for her unborn child -- and which might subject that child to long-term ills like allergies to peanuts and other foods.
"We have a tendency to beat pregnant women over the head with 'do this, don't do this,'" said obstetrician-gynecologist Dr. Laura Riley, medical director of labor and delivery at the Harvard-affiliated Massachusetts General Hospital. "We always want people to have a balanced diet that includes protein, fat and carbohydrates. We don't think pregnant women should take any one thing out of their diet."
But just as dietary advice for weight loss changes as new scientific information becomes available, so, too, does dietary advice for moms-to-be about how their eating shapes their future sons' and daughters' health.
The advice has been particularly tricky with respect to peanut allergy, a potentially fatal condition that affects an estimated 1 percent to 2 percent of children. The incidence has gone up in the last decade, although scientists can't say why.
From 1998 to 2000, the American Academy of Pediatrics and the British Committee on Toxicology recommended that in families where parents or siblings have allergies, women avoid peanuts during pregnancy and breast-feeding. But the data for these recommendations was scant and scientific studies yielded conflicting findings: Some said early exposure might be protective, others, harmful.
In 2008, the AAP reversed its position. Similarly, the European panel reversed its recommendation to stay away from peanuts during pregnancy and breastfeeding.
It now appears that in families with lots of allergies, it makes some sense for mothers-to-be to go easy on the peanuts, because of new research suggesting heavy consumption, particularly late in pregnancy, might set the stage for peanut allergies.
But for most families, doctors say there's no evidence that pregnant moms' peanut eating will produce an allergic baby -- or that avoiding peanuts will guarantee a healthier one.
To help clarify the issues, the Consortium of Food Allergy Research studied the relationship between maternal diet and childhood allergies. The researchers, led by Dr. Scott H. Sicherer of the Jaffe Food Allergy Institute at Mount Sinai School of Medicine in New York, followed 512 infants with food allergies to see if they became allergic to peanuts over time.
The investigators from Mount Sinai, Duke University in Durham, N.C., Johns Hopkins in Baltimore, National Jewish Health in Denver and Arkansas Children's Hospital in Little Rock, also asked the mothers about their prenatal eating.
In results published online Oct. 29 in the Journal of Allergy and Clinical Immunology, which will appear in the December print issue, they reported that the more that a mom consumed peanuts in the third trimester of her pregnancy, the greater the chances her infant would test positive for sensitivity to peanuts.
However, sensitivity doesn't equate to peanut allergy, "just an increased risk," Sicherer said.
At enrollment, the children were ages 3 months to 15 months, too young for food challenges typically used to establish allergies. The study authors said the youngsters would have to be monitored over time to determine if they developed peanut allergies later.