Birth Weights Decline In U.S.

Birth weights in the United States are on the decline, a study has found. The report, released Thursday, found a small but significant decrease in average birth weights from 1990 to 2005, for reasons that scientists say are unclear.

The numbers, published in the February issue of the journal Obstetrics & Gynecology, mark a shift from earlier reports that noted a rise in birth weights in the latter part of the 20th century.