Healthy full-term babies born in the United States today weigh an average of three ounces less than those born at term (39 to 42 weeks gestation) 20 years ago, researchers from Harvard Medical School have found.
However, the scientists say they do not have a full explanation for the lighter babes – increased Cesarean sections and pregnancy complications are apparently not the cause.
The report by Harvard researchers, published in the February issue of Obstetrics & Gynecologyalso found that that the length of gestation has shortened by about 2.5 days even in term births over the last two decades.
The lower average full term birth weight is explained at least in part by the earlier births, study authors say. The study team collected data on almost 37 million U.S. singleton full-term deliveries between 1990 and 2005 for their analysis.