THE anti-impotence drug Viagra may help make babies-but not in the way you think. The little blue pill might also help some infertile women get pregnant, according to researchers in Nevada.
Geoffrey Sher, of the Sher Institute for Reproductive Medicine in Las Vegas, has identified a class of women who seem to have trouble getting pregnant even when a perfect embryo is implanted directly into their uterus. The causes are various: some have infections or fibroids. Others have mothers who used the drug diethylstilboestrol (DES) to prevent miscarriages, now banned because it has been found to be a potent carcinogen.
But all the women had one thing in common-uterine linings so thin that healthy embryos refuse to implant. In most healthy women the uterine lining is at least 8 millimetres thick by the time they ovulate. Many of Sher's patients had uterine linings half that. "It all seemed to be related to the paucity of blood to the uterine wall through muscle tissue," he says.
Sher experimented with ways of getting more blood to the uterus. He asked some of his patients to wear nitroglycerine patches, known to stimulate the release of nitric oxide which relaxes blood vessel walls. While the patches did seem to help women get pregnant, the side effects, which included headaches, nausea and sudden drops in blood pressure, were intolerable. "They hated us," he says. But when the anti-impotence drug Viagra came on the market, Sher saw its potential. Like nitroglycerine, Viagra boosts the dilating effects of nitric oxide on blood vessels. And few side effects have been reported.
Sher recruited four women who had had at least three previous failed attempts at artificial conception. He measured their baseline blood flow to the uterus as well as the thickness of their uterine linings, which in all cases was less than 4 millimetres. Then he asked them to use specially formulated vaginal suppositories made from 25 milligrams of Viagra four times a day for a week. Earlier placebo suppositories had no effect, but Viagra greatly improved the blood flow and the quality of the uterine lining, he says. With thicker uterine linings, implantation is much more likely to be successful. In Sher's study, three of the four women subsequently became pregnant, and two have already delivered healthy babies.
Sher warns that the findings are preliminary, especially since nitric oxide can be harmful to embryos. He allowed a week to elapse between the last Viagra suppository and implanting the embryos, even though he thinks the nitric oxide clears out of the system more quickly. "We believe it's hours not days," he says. Sher hopes that the drug will make it possible for women with this form of infertility to conceive naturally and avoid IVF altogether.
Reporter: Alison Motluk
Source: Human Reproduction (vol 15, p 806)
New Scientist issue: 8 April 2000
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