Female mice given marijuana during pregnancy produced sexually crippled male offspring, two University of Texas researchers have found.

The researchers found their results sufficiently alarming to conclude that "no woman who is pregnant or plans to be pregnant should use marijuana in any amount."

The scientists -- Drs. Susan Dalterio and Andrzej Bartke of the University of Texas Health Science Center in San Antonio -- base the conclusion on studies of mice that show "significantly suppressed copulatory activity" in young adult sons of marijuana-dosed mothers.

Many other marijuana effects in mice have been confirmed in humans. But given the slower development of human sex organs, this one would take 15 to 20 years to check in human males.

"That's all the more reason for not taking any chance now," Dalterio said in an interview yesterday.

Not only is there an apparent effect, she explained, but also marijuana commonly contains contaminants, "things sprayed on the plants and who knows what else," that may harm the fetuses.

The Texas result was published in the current issue of the weekly journal Science. It follows other studies that indicate that regular, heavy marijuana use by males, on the order of several cigarettes daily, may make them impotent or cut their sperm output and sex drive.

Dalterio said, "this effect right now seems reversible if the male stops daily use, though we've only just begun to look at more subtle changes that seem more long-lasting."

The effect on male offspring when a mother uses the drug could be permanent, however, if human beings are to any degree like the mice she studied.

These young adult rodents commonly suffered decreases in the size of their testes, deficiencies of male hormone, impaired pituitary gland and gonad function and, when they were introduced to young females, poor sexual abilities. They were generally slow to mount females, they did so less than normal males and they often quit before completion.

Dalterio and Bartke gave 17 mice in all oral doses of THC (tetrahydrocannabinol), one active ingredient of marijuana; 20, cannabinol, a simpler constituent, and a group of 28 control mice no such chemicals. On the average, the mice that got the marijuana chemicals were only half as active sexually as normal animals.

The doses the scientists gave were, on a mouse-sized scale, comparable on a human scale to those that might be absorbed by a "heavy daily user of a decent grade marijuana," Dalterio reported.

"That doesn't mean such doses are uncommon," she said. "In New York City, for example, the current statistics on high school students show that a good percentage who smoke daily smoke six to 20 joints a day."

But even persons who smoke much less, she said, may produce "subtler effects" on their offsprings, and "probably nobody would ever know their cause."

Results like these should not be confused with some of the scare stories and exaggerations about marijuana that were circulated when the drug first came into wide use, she maintained.

She said some earlier researchers gave animals unrealistic doses and gave them in ways, such as injections, that did not resemble human use.

"We gave the chemicals orally because it's very hard to get mice to smoke," she said. "But smoking would be an even more efficient" -- hence even more damaging -- "way to get these chemicals into the bloodstream."