Study: Birth Defects Decrease Survival, Childbirth, Boost Risk Of Similar Defects

April 08, 1999

CHAPEL HILL - A new study of nearly a half million girls and women shows that those born with birth defects are less likely to survive, especially during the first years of life, than others born without them. Survival is lowest for such catastrophic conditions as anencephaly, hydrocephalus, other syndromes and central nervous system irregularities and highest for cleft palate and lip, clubfoot and malformations of skin, hair, nails and genitals.

Women with birth defects also are generally less likely to have children than others but face an increased risk of bearing offspring with the same problem, the research shows. Investigators found no higher-than-normal chance that an infant would have a different birth defect from his or her mother.

A report on the findings appears in Thursday's issue (April 8) of the New England Journal of Medicine. Authors are Drs. Rolv Skjaerven and Rolv T. Lie of the University of Bergen and Dr. Allen Wilcox, chief of the National Institute of Environmental Health Sciences' epidemiology branch and a University of North Carolina at Chapel Hill School of Public Health faculty member..

The three studied 8,192 women and adolescent girls with birth defects and 451,241 others listed in the Medical Birth Registry of Norway as being born between 1967 and 1982. Although impaired physical development during pregnancy is known to boost a baby's chance of death after birth and during infancy, investigators conducted their analysis since less is known about later survival and reproduction. Also, no one has assessed the risk of dissimilar defects in the children of such women in detail.

Among subjects with defects, 80 percent survived to age 15 compared with 98 percent of those without birth anomalies, researchers found. Among surviving subjects, 53 percent of those with defects bore at least one infant by age 30 compared with 67 percent of those born normal.

Affected women were a third less likely to give birth by age 30 than unaffected women. Children of subjects with birth defects overall faced a 60 percent higher risk of having birth defects themselves.

"This increased risk was confined entirely to the specific defect carried by the mother, with the relative risk of recurrence varying from 5.5 to 82 (times) according to the defect," the authors wrote. "In contrast, there was no increase in the risk of having an infant with a different type of defect."

Deaths among those with birth defects were 15 times as high in the first year of life and 12 times as high in the second year as among the others, they said. The relative risk decreased with age but was still more than four times higher among children ages 10 to 14.

"Although the subjects with birth defects had a risk of bearing children with birth defects that was 1.6 times the risk among those without birth defects, these subjects constituted only about 1 percent of the women who gave birth, the scientists said. "Thus, the higher risk among the subjects with birth defects accounted for only 5 of 1,000 birth defects in the next generation, according to an estimate."

Twenty-six women with birth defects had infants with the same defects as compared with an expected number of just under four, they found. Maternal defects that recurred in the children were cleft palate, cleft lip, clubfoot and malformed limbs.

"Among the children of the mothers with these birth defects as compared with the children of the mothers with no defects, the relative risks were as follows: cleft palate, 82; cleft lip, 38; clubfoot, 5.5; and limb defects, 5.6," the authors wrote.

The Norwegian Research Council supported the new study.
Note: Wilcox can be reached at 919-541-4660 until Tuesday night when he will be gone for a week.

University of North Carolina at Chapel Hill

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