Alcohol Tied to Unborns’ Brain Damage
WASHINGTON — A single drinking binge by a pregnant woman can be enough to permanently damage the brain of her unborn child, according to a new study of the effects of alcohol on babies.
Although experiments in the study were conducted on laboratory rats, experts said the findings offer an explanation of why children born to drinking mothers can suffer learning disabilities and other brain disorders.
The study indicates that rats, and presumably humans, are most susceptible to alcohol-related neurological damage during a period when developing brain cells are furiously building the connections needed for memory, learning and thought. In humans, this brain growth spurt starts in the sixth month of gestation and continues for two years after birth. In rats, it comes in the two weeks after birth.
“We call this a brain growth spurt period,†said Dr. John W. Olney, a researcher at Washington University School of Medicine in St. Louis and senior author of the study appearing today in the journal Science.
During this brain growth spurt, said Olney, a single prolonged contact with alcohol--lasting for four hours or more--is enough to kill vast numbers of brain cells.
“There is a massive wave of cell suicide after the brain is exposed to ethanol [alcohol],†said Olney. “The cells die by the millions and millions.â€
During the brain growth spurt, called synaptogenesis, brain cells must receive a balanced signal from two types of neurotransmitter chemicals, glutamate and GABA, he said. If this signal is disrupted, the developing brain cells are programmed to commit suicide. This is the body’s way of eliminating surplus cells.
But, based on the rat studies, alcohol severely disrupts the glutamate-GABA signals and this, in turn, causes nerve cell suicide at about 15 times the normal rate, he said.
Neuron cells that normally die during brain development are about 1.5% of the total, but in rat pups exposed to alcohol just days after birth, said Olney, the dead neurons ranged from 5% to 30% of the total.
“Our study showed that it only requires one round of intoxication of about four hours for this to occur,†said Olney.
The “binge†used in the study gave the rats a blood-alcohol level of 0.20, or 200 milligrams of alcohol per deciliter of blood. Such a level in people is twice the legal standard of drunkenness in many states.
A 1996 study by the Institute of Medicine showed that about 20% of women who drink do not stop during pregnancy. About 1 in every 1,000 babies born in the United States suffer from fetal alcohol syndrome, a disorder caused by exposure to alcohol in the womb. The disorder can cause stunted growth, along with memory and learning problems.
Olney said pregnant women need not be anxious about past, moderate alcohol drinking.
“One glass of wine at dinner is unlikely to cause the damage, but we cannot say that any added intake would be safe,†he said. “The most prudent policy would be to have no alcohol during pregnancy.â€
The connection between brain cell death and disruption of the glutamate-GABA signals also prompts concern about common drugs used on children, said Olney.
Most anesthesia drugs in pediatric surgery, he said, disrupt either glutamate or GABA in the brain. This means that surgery using these drugs might increase the risk of brain damage for children under the age of 2.
“It will be important to carefully reevaluate how these drugs are used in pediatric medicine,†said Olney. He suggested the need for studies to establish safety guidelines for use of these drugs on young children.
