Low calorie diet at conception may be linked to pre-term birth

April 29, 2003 in Nutrition Topics in the News, Pregnancy and Breastfeeding

Low calorie diet at conception may be linked to pre-term birth

Sheep that are fed a modestly low-calorie diet at the time they conceive tend to be at higher risk of delivering prematurely, suggesting one potential reason pre-term births occur. In humans, preemies are at greater risk of mental and physical problems, and most of the time, the reason for pre-term birth is unknown.

The current study findings, if applicable to humans, offer a potential explanation for some premature births, say researchers of the University of Auckland in New Zealand and his colleagues.

Based on these results, women of childbearing age should eat a healthy, balanced diet and should avoid any extremes of food intake. During the study, the researchers placed 10 sheep on a reduced-calorie diet that lasted from 60 days before conception to 30 days after. The diet aimed to cause a 15-percent drop in the animals' body weight.

While a decrease in body weight by 15 percent may seem drastic, the sheep's diet was only "moderately restricted," and sheep often experience similar changes in body weight as a result of changes in pasture conditions and other factors. Normal pregnancies in sheep last 145 days. However, sheep that were fed a restricted cuisine delivered lambs an average of seven days earlier than sheep that conceived during a period of normal eating.

Just why cutting calories might influence prematurity remains unclear.

Researchers speculate that the mother may send a "signal of some sort" that tells the developing embryo about its nutritional environment. If this nutritional environment is poor, the embryo may modify "developmental trajectories" like growth rate and length of gestation. So if the prevailing nutritional environment is poor, the fetus may set itself to deliver earlier to ensure that it doesn't outgrow the available nutrient supply in late gestation.

The researchers added that, if these findings apply to humans, they do not believe that women who are relatively undernourished when they conceive might be able to lower the risk of prematurity by eating more during pregnancy. They believe that the fetus is setting a developmental process in response to a signal early in gestation and, once this is set, it cannot be reset by increasing nutrition later.

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