In the 1980's, so-called "crack babies" made headlines by demonstrating the destructive effects of crack cocaine in the womb. A 2005 study suggests that the popular club drug crystal meth could damage a fetus with even a single dose.
How a hit of meth impacts a baby. I’m Bob Hirshon and this is Science Update.
A single hit of the drug crystal meth may be enough to cause permanent birth defects. That's according to University of Toronto pharmacologist Peter Wells, who led a study using pregnant mice. Just one dose of the drug led to poor motor coordination and other neurological problems in the mice's offspring.
Why is meth so harmful? Wells says the drug promotes the formation of free radicals. They're destructive forms of oxygen that damage DNA.
And the fetus is uniquely deficient in pathways that will protect you from free radicals.
So fetuses may be more vulnerable to meth's harmful effects than their mothers. And given that meth is popular with young women in both urban nightclubs and rural communities, Wells says it's important to tell them of the potential risk. I'm Bob Hirshon for AAAS, the Science Society.
Making Sense of the Research
Using any kind of drug, even many over-the-counter medications, during pregnancy can be bad news. That's because whatever the mother takes into her body goes into the fetus' body as well. Since the fetus is much smaller, and because it's doing the critical business of building brand-new tissues and organs, it's much more sensitive to the effects of chemicals. Examples of these effects include fetal alcohol syndrome (mental and physical impairments caused by drinking during pregnancy), newborn addictions to drugs like cocaine, and serious, often fatal deformities caused by the infamous drug Thalidomide, a sleep aid prescribed to thousands of pregnant women in the 1950's and early '60s.
However, it usually takes at least a few exposures to a harmful drug to have a serious impact on a fetus. For instance, an occasional half-glass of wine during pregnancy won't cause fetal alcohol syndrome. So it's striking that even one relatively small dose of crystal meth had such serious effects in this experiment.
What's more, the fetal mice were vulnerable to meth whether the mothers were given the drug early or late in the pregnancy. But while the baby mice had the same kind of poor motor skills that adult mice develop when they're given crystal meth, the physical damage seems to be different. Mice given crystal meth as adults develop obvious brain damage; the researchers didn't see that in the baby mice. Instead, they suspect that damage to fetal DNA by free radicals caused the impairments. In fact, they found evidence of free radical damage in the DNA of both baby mice and adult mice that had been exposed to the drug.
So how does this apply to humans? Although mouse and human bodies work in similar ways, obviously the researchers can't simply repeat the experiment in human fetuses. It's well established that crystal meth use can lead to birth defects; the question is whether a single dose is as powerful in humans as it is in the mice. Normally, the answer is to look in existing medical records for women who used the drug. But finding women who used crystal meth once, and only once, in their pregnancy could be difficult; also, many women who used crystal meth may have also used other drugs, which could make it difficult to determine the cause of any birth defects that followed.
Even if they can't be confirmed in humans, the findings are alarming. Because crystal meth can be made in home labs from ordinary ingredients, it's a drug that cuts across many social and economic groups. It's also a popular "club drug" among women in their teens and twenties. Since these women are of prime childbearing age, and since crystal meth can stimulate one's sex drive, the result may be pregnancies that are not only unintended but also carry an extremely high risk of birth defects.
Now try and answer these questions:
- It was already known that crystal meth can cause birth defects. What's new about these findings?
- How did the effects of crystal meth on the fetal mice differ from the effects on adult mice?
- Why is it hard to confirm this in humans?
- If crystal meth harms fetuses by creating free radicals, what else might researchers look for as potential causes of birth defects?
Thalidomide Gets a Second Chance, from the National Institutes of Health Office of Science Education, features the history of the drug thalidomide and its future uses in medicine.
In the National Geographic News article Pesticides, Parasites, and Frog Deformities, read about studies to determine the cause of physical abnormalities in frogs.