After excluding chromosomal abnormalities, a recent study found that women ages 35 years and older had a decreased risk of having a child with any major physical birth defects (congenital malformation).
The researchers discovered that these women were less likely to have babies with brain, kidney and abdominal wall defects compared to the women who were under the age of 35 years old.
The lead author of this study was Katherine Goetzinger, MD, MSCI, from the Department of Obstetrics & Gynecology at Washington University in St. Louis, Missouri.
Advanced maternal age, usually defined as 35 and older, is a strong risk factor for having a child with a chromosomal abnormality, such as Down syndrome or trisomy 18. This research looked at physical birth defects that were not related to cell division.
The study included 76,156 pregnant women who came in for a second routine ultrasound at Washington University. A total of 55,353 women were below 35 years old, and 20,803 were 35 years of age or older and were considered to be of 'advanced maternal age' (AMA).
All pregnancies were single-fetus and did not have chromosomal defects (such as Down Syndrome).
The findings showed that 1,804 (2.4 percent) of all the fetuses had some type of major anomaly — with 1.7 percent of fetuses in the AMA group having a major anomaly compared to 2.6 percent in the under 35 years old group.
AMA was associated with a 41 percent decreased risk of major fetal anomaly compared to pregnant women who were younger than 35 years old.
The researchers found that 496 fetuses had a central nervous system anomaly, with 0.4 percent of the AMA group showing this type of anomaly versus 0.7 percent of the under 35 years old group.
A total of 226 fetuses had a kidney anomaly. Of the AMA group, 0.2 percent had this type of anomaly versus 0.3 percent of the under 35 years old group.