Causing permanent damage (Image: Jamie Grill/Getty)

Drinking too much during pregnancy can harm offspring permanently. Now experiments in mice suggest this may be because alcohol chemically alters the fetus’s DNA, affecting how genes are expressed.

It’s well known that fetal alcohol syndrome occurs when pregnant women drink excessively and causes behavioural and physical harm to the child after birth. But we know little about the molecular mechanisms underlying the condition.

Previous studies have shown that factors in the mother’s environment during pregnancy can cause “epigenetic” modifications to the fetus’s DNA. These don’t alter the genetic code itself but might switch certain genes on or off, or increase or decrease their expression.


To see whether a mother’s alcohol consumption might affect the way her child’s genes are expressed, Suyinn Chong at the Queensland Institute of Medical Research in Herston, Australia, and her colleagues turned to mice with genes for brown and yellow fur that are known to be modified by environmentally induced epigenetic changes.

Fur coat

“It’s a good model to use because you can tell whether a mouse’s environment is affecting the expression of its genes just by looking at its coat colour,” says Chong.

Females with two copies of the gene for yellow fur were mated with males that had two copies of the brown fur gene. This will yield a predictable ratio of brown, yellow and mottled offspring – unless epigenetic factors are affecting gene expression.

Pregnant mice were given alcohol instead of water to drink freely during the first half of pregnancy. Their blood alcohol levels were around 0.12 per cent – the equivalent in a human of around one-and-a-half times the legal driving limit in the UK and US.

When the team looked at the newborn mice, they counted twice as many brown mice as they expected. “This means that the alcohol was affecting the epigenome of the mice – controlling whether their genes were switched on or off,” says Chong.

Liver changes

Because the gene for fur colour isn’t relevant to humans, the team next studied the DNA in the mice’s liver cells. They spotted 15 genes that had been altered to either increase or decrease their activity in mice whose mums drank during pregnancy.

Chong isn’t sure what these genes do, but the changes show that the epigenetic influence of alcohol isn’t limited to genes that affect fur, and suggest that a similar mechanism could be at work in humans.

Infant mice that had been exposed to alcohol in the womb also had some of the symptoms of human fetal alcohol syndrome, such as a lower body weight and smaller skulls.

This suggests that if women drink too much in pregnancy, epigenetic changes may cause some of the permanent symptoms seen in fetal alcohol syndrome in their children.

Early help

In some cases, epigenetic changes in people seem to be passed on to subsequent generations. Chong says she doesn’t know whether epigenetic modifications due to alcohol are passed onto the next generation of mice, but she hopes to find out in upcoming studies.

“This is an important development in understanding how alcohol exposure in the uterus causes lifelong detrimental effects in the offspring,” says Michele Ramsay, a geneticist at the University of the Witwatersrand in Johannesburg, South Africa.

If Chong’s group can confirm that fetal alcohol syndrome causes epigenetic changes in humans too, it might allow the syndrome to be spotted earlier on in life.

“If we find specific genes have been affected by alcohol exposure, we could potentially screen newborns for the syndrome so that they can be offered social care early in life,” says Chong. “But it’s still early days.”

Journal reference: PLoS Genetics, DOI: 10.1371/journal.pgen.1000811