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Genetics May Play Role in Alcohol-Related Birth Defects

Genetics may help explain why the children of some women who drink alcohol during pregnancy have birth defects and others do not.

A new study of mice has found that genetics may help explain why the children of some women who drink alcohol during pregnancy have birth defects and others do not.

The findings are published in the journal Alcoholism: Clinical & Experimental Research.

Consuming alcohol while pregnant can lead to teratogenesis, or the development of embryonic defects. The term "fetal alcohol spectrum disorders," or FASD, is used in the medical community to describe a variety of alcohol-exposure effects seen in about 1 percent of live births in the United States.

These effects include pre- and postnatal growth retardation, craniofacial anomalies, central nervous system dysfunction, hand or finger malformations, a number of different skeletal malformations and anomalies in the brain, eyes and kidney, according to Chris Downing, a research associate at the University of Colorado and corresponding author for the study.

"Some women who drink during pregnancy don't give birth to children with any of these observable deficits, but later on, their children develop a number of behavioral deficits including hyperactivity, attention deficits, learning problems and deficits in impulse control," Downing said in a press release announcing the study's findings.

"It is thought that these behavioral deficits are due to brain damage as result of in utero ethanol exposure, but correlating specific behavioral deficits with damage to specific brain areas is a work in progress. In addition, some women who drink during pregnancy have 'normal' children with no obvious deficits."

There are many factors that have been shown to contribute to the development of FASD, from the amount, timing and pattern of maternal alcohol consumption to demographic information like age, ethnicity, cultural factors and socioeconomic status.

"Using mice, we can control for all of these confounding variables," Downing said. "Within an inbred strain, all mice are virtually genetically identical, greater than 99.9 percent. When one looks at more than one inbred strain of mice, and all mice are housed and treated the same, differences between strains are taken as evidence of a genetic effect."

For the study, mice were given either alcohol or a placebo on their ninth day of pregnancy (roughly equivalent to the end of the first month of human gestation). Some mice that were exposed to alcohol in utero had severe fetal weight deficits, as well as digit, kidney, brain ventricle and vertebral malformation. But 129 mice showed no teratogenesis, while others showed varying degrees.

The findings hold several lessons for people, Downing said.

"Since genetic effects on prenatal alcohol phenotypes in mice have been demonstrated, and the mouse and human genomes are remarkably similar, it suggests genetics plays a role in humans as well," he said. "Human researchers need to begin to systematically investigate genetic factors mediating susceptibility and resistance to the effects of prenatal alcohol exposure."

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