New research indicates that many cases of prematurity—one of the strongest predictors for later academic, social, and behavioral problems—result from missing nutrients in mothers' diets before and at the time of conception.
Studying sheep, Frank Bloomfield and colleagues found that half of the animals put on a moderately restricted diet around the time of conception had premature offspring, compared to none of a control group allowed to eat a normal amount of food.
The researchers put 10 ewes on restricted diets for 60 days before they mated and 30 days afterward. The diet lowered the animals' body weight by 15 percent. Compared to 8 sheep fed normal diets, the "dieting" sheep delivered an average of one week earlier (139 days vs. 146 days). In addition, while both groups of offspring were of normal weight, the offspring of the limited-diet sheep were sicklier.
Peter Gluckman, head of the institute that sponsored the study, commented that the research shows that "a mild, relatively uninteresting and relatively brief incident at the beginning of pregnancy can change something as profound as the length of pregnancy."
The researchers say that in the sheep fed restricted diets, levels of two hormones—cortisol and adrenocorticotropin—surged earlier in pregnancy than is normal. These hormones play a role in maturation of the lungs, liver, and other organs in the developing fetus. The researchers speculate that early in embryonic development the mother's body sends a "signal of some sort" that informs the fetus about its nutritional status, and that the embryo in turn may modify its growth rate and gestation period. They also theorize that it may be impossible to alter this developmental trajectory afterward, as their sheep were well-fed later in pregnancy but still delivered premature offspring.
The researchers say that based on their findings, "women of child- bearing age should eat a healthy, balanced diet and should avoid any extremes of food intake."
"Hungry ewes deliver offspring early," Frank Bloomfield et al., Science, Vol. 300, April 25, 2003, 561-2. Address: Frank Bloomfield, The Liggins Institute, University of Auckland, Private Bag 92019, Auckland, New Zealand.
"Hungry ewes deliver early offspring," ScienceNow, April 24, 2003.
"Low-cal diet at conception linked to preterm birth," Reuters Health, April 24, 2003.