Researchers say couples trying to get pregnant through in vitro fertilization (IVF) could up their chances of success if they just keep trying.

But according to data in the researchers’ study from several fertility clinics in Western Australia, many don’t end up pregnant.

Between 1993 and 2002, half of more than 5,000 women who started IVF treatment went through two or fewer cycles. The chances of giving birth to a live baby as a result of IVF were 58 percent for women in their 20s, but only 22 percent for women aged 40 to 44.

Based on calculations, the researchers estimate that upping the number of IVF cycles would boost success rates at least up until five attempts.

“The results of this study suggest that IVF has the potential to be more effective if women, especially those over 35, are able to undertake more than the usual two to three cycles,” Louise Stewart of the University of Western Australia in Crawley and colleagues write in the journal Fertility and Sterility. (One of the authors is on the fertility advisory board of Merck Serono Australia and Schering-Plough Australia, both of whom make fertility drugs.)

But the study also shows that a number of women went on to give birth to live babies after they stopped IVF treatment. Including those births, 79 percent of the women who started IVF in their 20s ended up with successful pregnancies, compared to a third of those in their early 40s.

One fertility expert who spoke with Reuters Health questioned the new findings, especially the way the researchers had calculated the success rates with more IVF cycles.

Because few women go through many cycles, such estimates quickly become shaky, said Dr. Mitchell P. Rosen of the University of California, San Francisco, Center for Reproductive Health.

“It is pretty obvious that the number of cycles that you do adds to the likelihood of success, but it gets smaller every time,” he said. “You have to look at each case independently. Are we seeing benefits or are we just spinning our wheels?”

In the U.S., one IVF cycle may cost up to $15,000 and each failure will take a mental toll. Rosen said he had seen couples try as many as 11 times.

“At some point the psychological side effects and the cost become prohibitive,” he told Reuters Health. The good news, he said, is that “people who do quit IVF still have a chance.”

SOURCE: Fertility and Sterility, online February 14, 2011.