Fetal Alcohol Syndrome
July 28, 2004
New research reveals how heavy drinking during the third trimester of pregnancy can cause brain damage in babies.
Fetal alcohol syndrome (FAS) is a permanent condition that can occur in a newborn if a woman drinks alcohol during pregnancy. It's often characterized by abnormal facial features, growth retardation, and central nervous system problems. Children with FAS may have physical disabilities, but the damage may also be limited to problems with learning, memory, attention, and problem solving.
"Alcohol is the most widely abused drug in the Western world," says Ann Streissguth, director of the Fetal Alcohol and Drug Unit at the University of Washington. "In our work we find that one per 100 live births are affected by prenatal alcohol exposure and that is so important. That makes it the largest known cause of mental retardation and developmental disabilities."
Experts have long warned expectant mothers to not drink, especially early in pregnancy, when the baby's body is forming. John Olney, professor of psychiatry and neuropathology at Washington University in St. Louis, is studying how alcohol hurts the fetal brain in later in the pregnancyby triggering nerve cells, which are just forming connections, to commit suicide.
"The brain growth spurt period begins about mid-gestation, about the middle of pregnancy," says Olney. "The nerve cells in the brain make connections with one another. We also call this brain growth spurt period the period of synaptogenesis, meaning the brain cells are making connections with one another, so it's the period in which the brains cells are getting themselves connected into networks." Synaptogenesis takes place in the human brain from the sixth month of gestation through a few years after birth.
Studying the brains of newborn mice, which are developmentally similar to late-term human brains, Olney found that alcohol (as well as anesthetic drugs, such as sedatives) interferes with two neurotransmitters - glutamate and GABA. This disruption blocks signals between nerve cells so they can't make connections. The cells are programmed to commit suicide - called apoptosis - if these connections aren't made. "When it's apparent that [cells] are not going to make their connections, they get an internal signal that says 'kill yourself' and they proceed to do so," Olney explains. "This effect is one in which nerve cells throughout the brain, a certain percentage in each brain region, are simply being quietly deleted."
The extent of the damage still remains a mystery, but Olney says when it comes to FAS, timing is everything. "The facial malformations occur at a different time in development than the central nervous system disturbances," he says. "It's entirely possible that you might have a person with the facial malformations but not the central nervous system effects, because the mother, after learning she was pregnant but having already had exposure to alcohol during an earlier period, [caused] the facial malformations. Then she stopped drinking [and] therefore didn't incur the central nervous system disturbances. The timing of exposure could be late in pregnancy rather than early in pregnancy, and if that were the case, then the offspring would have central nervous system disturbances but no facial malformations."
Ann Streissguth stresses that this research reminds us that alcohol can cause damage at any stage of pregnancy, not just early on. "If you could stop women from drinking during pregnancy, you could prevent fetal alcohol syndrome," she says. "That's a message we've known about since 1981 when the surgeon general first recommended it and it has been recommended by many surgeons general since - but each generation needs to hear it again because alcohol is so commonly used."
This research was presented at 2004 Annual Meeting of the American Association for the Advancement of Science (AAAS) and appeared in the 2002 issue of Brain Pathology. It was funded by the National Institutes of Health.