Is there any research on the benefits of women taking Viagra to increase the thickness of a thin uterine wall? If so, what kind of success rate does this have for conceiving and giving birth to healthy babies?

J.J.A.

A recent article in the journal Human Reproduction suggests that the use of Viagra may enhance the development of the uterine lining (endometrium) in patients who did not respond well to traditional infertility treatment. While the article reported the beneficial outcome occurring for a handful of patients, we can't really call this report a clinical trial -- that is, it is not a controlled study showing that the treatment is safe and effective. Rather, it is a case report, and as such should be taken with a good dose of caution. It provides no evidence that allows us to predict success, and there is no way to tell whether the reported successes simply occurred by chance. But it does suggest some very creative thinking.

Women who fail to conceive because of a poor uterine lining have to date been difficult to treat. When we determine that the uterine lining has failed to develop properly, the first questions we ask are whether an infection is present and whether the estrogen level is high enough. Also, if the woman is taking clomiphene (Clomid), a potent antiestrogen often used to induce ovulation, the thin lining may be as a result of that medication. But low estrogen, infection and clomiphene can not explain all cases of poor endometrial development.

We know that as the follicles (the structures that house eggs) develop and estrogen levels rise, the blood supply to the uterus increases. This occurs due to the body's natural production of nitric oxide (NO) a potent dilator of blood vessels. This process is similar to the way nitroglycerine dilates blood vessels to lessen chest pain in heart patients. We also know that smokers have less NO. Also, in women with PCOS (polycystic ovary syndrome) or type II diabetes, the blood vessels are less likely to dilate in response to NO. Some believe that lower levels of NO or failure to respond to NO may result in infertility and/or miscarriage.

So why not give NO, or substances that do a similar job? This has been tried. Studies looking at improving the uterine lining have used nitroglycerin patches, L-arginine dietary supplements and now Viagra with this purpose in mind. A recent well-designed clinical trial using L-arginine daily seemed to improve the results of IVF (in vitro fertilization) in a select group of women who had failed previously. Unfortunately, it is also known that too much NO can be toxic to the fetus if taken while pregnant.

More studies are needed to determine who are the best candidates for treatment with one of these agents. The risks need to be determined, and larger, well-designed clinical trials must be completed before this treatment is routinely adopted.