快猫短视频

THE anti-impotence drug Viagra may help make babies鈥攂ut 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鈥攗terine 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鈥檚 patients
had uterine linings half that. 鈥淚t all seemed to be related to the paucity of
blood to the uterine wall through muscle tissue,鈥� 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. 鈥淭hey hated us,鈥� 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鈥檚 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. 鈥淲e believe it鈥檚 hours not days,鈥� 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.