Scientists are trying to identify the chemical imbalances that occur in the wombs of women who consume alcohol during pregnancy and produce babies who are grossly stunted in growth.
Low birth weight and short stature are the key characteristics of the preventable disorder known as fetal alcohol syndrome. It can be produced by as few as one to two drinks daily, a 1984 National Institutes of Health study shows.
But even though scientists are aware of the approximate amount of alcohol required to cause the syndrome, they remain uncertain about what occurs chemically to stunt growth and trigger numerous other maladies often detected in children afflicted with the disorder.
"We have identified proteins that are produced by the placenta and now we are interested in what they do in normal pregnancy, how they are regulated and what happens when things go astray," said biologist Frank Talamantes of the University of California, Santa Cruz.
He said scientists have not fully understood the effects of alcohol in a developing fetus because growth is caused by a complex set of mechanisms. But work is under way in his lab centering on the role of several endocrine system proteins, hormones that among other functions influence growth and development.
"Placental lactogens (produced by the placenta) are among these hormones," Talamantes said. "Since we're interested in the role of these proteins, we'd like to know if their secretion is altered if the mother drinks a lot of alcohol."
In studies of mice, Talamantes has found that placental lactogens are involved in the stimulation of growth hormone.
"Growth hormone from the mother stimulates growth factors in the fetus which ultimately affect the growth of the fetus," Talamantes said. He noted that mice suffering from fetal alcohol syndrome cannot achieve growth potential dictated genetically because of prenatal chemical interference.
The biologist suggests there are at least three ways that consumption of alcoholic beverages may interfere with the secretion of crucial growth-related hormones.
When the hormones are released by the endocrine system, they seek out matching receptor molecules, and this "lock and key" combination between hormones and receptors may be blocked by alcohol.
"Another possibility for the lack of growth in the fetus is that the structure of the receptors may be altered as a result of the alcohol consumption," he said.
Maternal Nutrition a Factor
Talamantes said maternal nutrition is another factor that has to be considered because "many women who consume a lot of alcohol usually do not have a very good diet."
"One has to be careful in separating out the effects of fetal alcohol syndrome," he said. "I also have to ask if it is the alcohol itself causing these effects or is it the fact that they do not eat properly and the fetus is being stunted because it did not receive the proper amount of nutrients."
Talamantes also speculates that one reason for low birth weights--less than 5.5 pounds--is that hormones possibly inhibited by alcohol also serve the dual role of directing nutrients throughout the body.
Talamantes said he hopes to develop a way to detect fetal alcohol syndrome by measuring hormone levels in the womb.