In a study to be presented on Feb. 6 at 3 p.m. CST, at the Society for Maternal-Fetal Medicine’s annual meeting, The Pregnancy Meeting™, in New Orleans, researchers will report that women ages 35 and older are at a decreased risk of having a child with a major congenital malformation, after excluding chromosomal abnormalities.
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.
Abstract 34: Advanced Maternal Age and the Risk of Major Congenital Anomalies: Survival of the Fittest?
Authors: Katherine Goetzinger1, Anthony Shanks1, Anthony Odibo1, George Macones1, Alison Cahill1
1Washington University in St. Louis, Obstetrics & Gynecology, St. Louis, MO
Objective: Advanced maternal age (AMA) is a well-established risk factor for fetal chromosomal abnormalities secondary to defects in cell division; however, the relationship between AMA and major congenital anomalies remains unknown. The objective of this study was to determine if AMA is an independent risk factor for major congenital anomalies diagnosed at the time of second trimester anatomic survey, in the absence of aneuploidy.
Study Design: This is a retrospective cohort study of all patients with a singleton gestation presenting for second trimester anatomic survey over an 18 year period. Cases of aneuploidy were excluded. Study groups were defined by maternal age <35 versus ?35 years. The primary outcome was the presence of one or more major fetal anomalies diagnosed at second trimester ultrasound. Univariate and multivariate logistic regression analyses were used to estimate the risk of major fetal anomalies in women who were AMA. The distribution of fetal anomalies by organ system was also compared between the study groups.
Results: Of 76,156 euploid fetuses, 2.4% (n=1,804) were diagnosed with a major anomaly. There was a significant decrease in the incidence of major fetal anomalies with increasing maternal age until the threshold of age 35. (p<0.001) AMA was significantly associated with an overall decreased risk for major fetal anomalies (aOR 0.59, 95% CI 0.52-0.66) after controlling for potential confounders. Specifically, the incidence of central nervous system (CNS), renal, and abdominal wall anomalies were decreased in women ?35 years. This was contrasted by the similar rate of cardiac anomalies between the study groups. (Table)
Conclusion: AMA is associated with an overall decreased risk for major fetal congenital anomalies, driven by a decrease in CNS, renal and abdominal wall defects. These surprising findings may suggest that the “all or nothing” phenomenon plays a more robust role in embryonic development with advancing oocyte age, with anatomically normal fetuses being more likely to survive.