Nearly 7 million babies born between 1995 and 2000 were tracked for this study. Researchers found infants born between 24 and 31 weeks were at the highest risk for birth defects, five times more likely than full-term infants.
The most common birth defects in the group were with the central nervous system, like spina bifida, or cardiovascular defects such as a hole in the infant's heart. What caused the birth defects is not known.
This study was conducted by the CDC's National Center on Birth Defects and Developmental Disabilities.