In a finding that raises provocative questions about how a father's drug use might cause birth defects in his children, researchers have found that cocaine can attach itself to human sperm without impairing the sperm's survival or mobility.
The results, published today in the Journal of the American Medical Assn., suggest that sperm might carry cocaine or other toxins into an egg, triggering the kind of developmental problems in offspring already seen in animal studies.
The research sheds new light on the issue of the responsibility of fathers for the health of fetuses--at a time when some women have objected to law enforcement officials and employers placing the burden on mothers.
"It opens an entire new field in investigation of the potential role of the father . . . in the occurrence of birth defects in the offspring," said Dr. Ricardo A. Yazigi, a Temple University School of Medicine assistant professor and lead author of the paper.
The findings are highly preliminary, based on laboratory tests. They offer no conclusive proof that a father's cocaine use could damage a fetus. But if affirmed in further studies, the research could have significant public policy implications, experts said.
"So much work and effort has been pointed toward looking at the role of women and drug use on reproductive outcome," said Dr. Ira Chasnoff, head of a national research and education organization concerned with the effects of maternal drug use on newborns. ". . . If there is a role of men, we have to address it."
Alison Marshall, a Washington lawyer who has defended women accused of crimes for having exposed their fetuses to drugs, added, "This is the first study that I've seen that in any way concretely begins to suggest that in fact there is an effect (on newborn health) based on the cocaine use of males, pre-conception."
The research was prompted in part by animal studies that have shown that the offspring of male mice exposed to cocaine and methadone appear to have a higher risk of birth defects and neurological problems than the offspring of "drug-free" male mice.
No such studies have been done in humans, in part because of the difficulty of distinguishing the effects of a father's drug use from the effects of other factors. But one study suggests a father's alcohol consumption may contribute to developmental problems in a newborn.
Similarly, there appears to be a higher rate of developmental problems in the children of some men exposed to chemicals and heavy metals in the workplace. As examples, some researchers cite men exposed to lead and pesticides on the job.
"It's nothing that's absolutely new," said Kenneth Polakoski, a biochemist at Washington University in St. Louis who worked with Yazigi. "The male has been known to cause many different birth defects, from spontaneous abortion to neonatal mortality."
Polakoski said cocaine is unlikely to have any effect unless it is used less than two weeks before conception. He said the breakdown products of cocaine can be found in urine up to 10 or 12 days after use; after that, the traces disappear.
In their study, the researchers attempted to explore how cocaine or toxins might make their way to the developing fetus. They hypothesized that if cocaine could bind to sperm, it might be carried up the female reproductive tract and into the egg at fertilization.
To see if cocaine could bind to sperm, they incubated a mixture containing sperm taken from drug-free men with a fluid containing cocaine, simulating conditions in the body. When they later washed off the sperm and analyzed it, they found that the cocaine had bound tightly to it.
They conducted the experiment using different temperatures, incubation times, concentrations of cocaine and concentrations of sperm. They also analyzed the influence of the cocaine on the sperm's so-called motility, or spontaneous mobility, and viability, and could find no effects.
"The data show that cocaine does bind to sperm," said Dr. Randall R. Odem, a member of the group. ". . . I think caution needs to prevail, though, in that we haven't proved that this is the mechanism (that might cause birth defects) and that it exists in humans."
For example, it has yet to be shown that cocaine can actually be transported to the egg and can influence the development of the embryo. Yazigi said the group chose that hypothesis because it appeared to be the most likely explanation for the findings in animals.
"From a scientific point of view, it's a very exciting first step," said Chasnoff, president of the National Assn. for Perinatal Addiction Research and Education. ". . . We don't have nearly enough information on the impact of drug use on men's reproductive capabilities."
Marshall, who serves as counsel to Chasnoff's group, noted that many of the estimated 60 to 80 women prosecuted for having used drugs in pregnancy have argued that it is selective prosecution, unconstitutionally singling out women because of their reproductive capacity.
"Whether this means that men should be prosecuted . . . how do you get the evidence?" Marshall mused. "I think we're a long way from being able to establish in a real-life case that a newborn's birth defects were caused by the father's pre-conception use of cocaine."