Birth defects not involving chromosomes are more common among the offspring of teenage mothers than among older mothers, UK investigators have found.

Teenage mothers are known to have a higher risk of some “nonchromosomal” birth anomalies, they explain, but there is little information on the overall risk.

To investigate, Dr. M. Loane from University of Ulster, Jordanstown, and colleagues used data from EUROCAT, a network of population-based birth defect registers covering almost one third of births in Europe.

The overall prevalence of nonchromosomal birth defects was 22.4 per 1000 births, and it ranged from 26.5 per 1000 births among mothers who were younger than 20 years old, to 21.4 per 1000 births among mothers who were 35 to 39 years.

Teenage mothers were 6.3-times more likely than mothers who were 25 to 29 years old to have a baby born with a defective closure of the abdominal wall through which the intestines protrude - a condition called gastroschisis - and nearly 5-times more likely to have a baby born with malformations resulting from maternal infection during the first trimester.

The likelihood of two heart defects - tricuspid atresia and stenosis - was almost 3-times more common among teen mothers. The risk of anencephalus (a brain abnormality) and nervous system and digestive system anomalies was also higher in the adolescent moms.

Women aged 35 to 44 years were more likely than mothers aged 25 to 29 years to have infants with fetal alcohol syndrome, the researchers note, but they were less likely than younger women to have babies with nonchromosomal congenital anomalies.

“The maternal age pattern of risk differs between countries, suggesting that it is not biological age that is associated with risk of nonchromosomal congenital anomalies, but reproductive, social, ethnic, exposure, or lifestyle factors that have a different relationship with maternal age in different European countries,” the investigators point out.

Interventions, they conclude, are needed to reduce environmental risk factors for nonchromosomal birth defects, “giving special attention to young mothers among whom some risk factors are more prevalent.”

SOURCE: BJOG: An International Journal of Obstetrics and Gynaecology, July 2009.