Women 35 and older are at decreased risk to have anatomically abnormal child, study suggests

Advanced maternal age, traditionally defined as 35 and older, is a well-established risk factor for having a child with a chromosomal abnormality, such as Down syndrome. However, little information is available regarding the association between advanced maternal age and the risk for having a child with a major congenital malformation -- a physical defect present at birth that can involve different parts of the body, including but not limited to the heart, brain, kidney, bones or intestinal track.

In order to address this question, this retrospective study used obstetric and ultrasound information collected from over 76,000 women at the time they presented for their routine second trimester ultrasound at Washington University in St. Louis (Mo.). Researchers compared the incidence of having one or more major congenital malformations diagnosed at the time of ultrasound in women who were younger than 35 versus those women 35 years and older.

Also examined was the incidence of major malformations of women categorized by organ system including heart, brain and kidney. Overall, we found that advanced maternal age was associated with a 40 percent decreased risk of having a child with one or more major congenital malformations, after controlling for other risk factors. Specifically, the incidence of brain, kidney, and abdominal wall defects were decreased in this group of women, while the incidence of heart defects was unchanged.

"As more women are choosing to delay childbearing, they are faced with many increased pregnancy risks," said Katherine R. Goetzinger M.D., M.S.C.I., one of the study's researchers. "Findings from this study may provide some reassurance for these women regarding the likelihood of having an anatomically normal child."

Goetzinger, an assistant professor of maternal-fetal medicine at Washington University in St. Louis School of Medicine, also noted that it is possible that advanced maternal age conveys a "survival of the fittest" effect, in which anatomically normal fetuses are more likely to survive.