Prenatal drinking may boost baby's stress response

By Amy Norton

NEW YORK (Reuters Health) - Infants who were exposed to alcohol early in pregnancy may have an exaggerated stress response compared with other babies, researchers reported Monday.

It has been established that prenatal alcohol exposure can cause a range of lifelong problems, including impaired growth, physical and mental disabilities, and learning disorders. Some research, mostly in animals, has also suggested that alcohol affects the development of the complex systems that regulate the body's response to stress.

In the new study, researchers found that in general, the greater a mother's alcohol intake was in early pregnancy, the greater was her infant's reaction to stress, which included a more rapid heart rate, a greater surge in stress hormones and more emotional distress.

This increased "stress reactivity" is a potential risk factor for future emotional and cognitive problems, Dr. David W. Haley, the study's lead author, told Reuters Health.

What's more, he and his colleagues found that women's alcohol intake very early in pregnancy -- before they knew they were pregnant -- appeared key in their infants' stress responses.

"Based on these findings and the findings from other studies, mothers who are planning to become pregnant should abstain from alcohol to be safe," said Haley, an assistant professor of psychology at the University of Toronto in Canada.

The study, published in the journal Alcoholism: Clinical & Experimental Research, are based on tests of 55 five- to seven-month-old infants whose mothers were part of a larger alcohol intervention study.

The infants' stress responses were measured using a standard test called the "still-face" procedure, in which a parent faces the baby but remains still and unresponsive. This eventually upsets the infant, causing a rise in heart rate and levels of the stress hormone cortisol.

But Haley and his colleagues found that this stress response tended to be more dramatic as the infant's prenatal alcohol exposure increased.

On average, mothers in the study recalled having about two drinks a day in the weeks before they knew they were pregnant. They cut back significantly thereafter, but it was their drinking in those early days of pregnancy that appeared to affect infants' stress reactivity, the study found.

It's possible, according to Haley's team, that fetal alcohol exposure alters the development of the complex pathway between the brain and adrenal glands that regulates the body's stress response, including stress hormone secretion. Greater exposure to stress hormones may, in turn, affect infants' ongoing brain development.

"Our findings," the researchers write, "may have important implications for women who drink, even at what might be considered social levels, before pregnancy recognition, and for their children."

SOURCE: Alcoholism: Clinical & Experimental Research, December 2006.