THURSDAY, Oct. 29 (HealthDay News) -- Women who lie flat for 15 minutes after being artificially inseminated greatly boost their odds of becoming pregnant, new research suggests.

"Allowing women treated for subfertility with IUI [intrauterine insemination] to remain in supine position will yield a 50 percent higher chance at conceiving," said Inge Custers, lead author of a study to be published online Oct. 30 in the BMJ.

Custers and colleagues aren't sure why this simple step yields better results, but they hypothesize that the supine position prevents sperm "leakage" from the vagina.

IUI involves placing sperm directly into the uterus, where conception then hopefully takes place. It differs from in vitro fertilization, which involves fertilizing the egg in a test tube before implanting the embryo in the uterus.

According to the editorial, IUI offers several benefits, including minimal drug involvement and low cost. It is also more accessible, being offered in smaller clinics. A main downside is a pregnancy rate lower than that achieved by in vitro fertilization.

IUI remains one of the most common fertility treatments worldwide, the study authors stated.

This study involved almost 400 couples in The Netherlands who were undergoing intrauterine insemination. The women were randomized to lie prone for 15 minutes after insemination or to get up right away.

Twenty-seven percent of women who stayed still for 15 minutes became pregnant vs. 18 percent in the other group. Live birth rates followed a similar trend: 27 percent in the first group and 17 percent in the control group.

The main problem with this method would be taking up more time and space at fertility clinics.

On the other hand, achieving conception the first time around would mean fewer repeat visitors, the experts noted.

"Over the years, subfertility is an increasing problem, which causes higher demands on busy offices, trying to treat as many patients as possible," said Custers, a student and registrar at the Centre for Reproductive Medicine at the Academic Medical Centre in Amsterdam. "With increased efficacy of the procedure, these women will therefore not return for subsequent cycles. A positive effect of this study was observed in The Netherlands: more and more women have been allowed this treatment strategy. Whether this will be implemented globally remains to be seen."

One expert said it wasn't yet clear whether this was the best way to maximize pregnancy odds.

First of all, it's not known what common practice is currently in clinics: lying down for 5, 10, 15 minutes or longer, said Dr. Peter McGovern, director of the division of reproductive endocrinology and infertility at Hackensack University Medical Center in New Jersey.

"These authors didn't test other times," he said. "And studies in the past found that sperm deposited in the vagina could be found at the end of the fallopian tubes within 5 minutes. I think probably any time period over 5 minutes would probably give you the same difference. It's probably a good idea to have people lay flat for some period of time as opposed to just leaping up."

Another expert agreed.

The Dutch study's conclusions are "plausible," said Dr. Roger Lobo, president-elect of the American Society of Reproductive Medicine and professor of obstetrics and gynecology at Columbia University, although the 15-minute time span used in the study does appear "artificial."

"Five minutes is probably sufficient," he said. "Sperm travels very, very rapidly. If you get up within the minute there may be some leakage."

"In our practice I've never heard of anyone who gets up immediately," Lobo said. "The standard is 10 minutes. Women who are asked to get up immediately may have a stress response." Volume of sperm also plays a role with more sperm upping the odds of pregnancy, he added.

More information

There's more on infertility at the American Society of Reproductive Medicine.

SOURCES: Inge Custers, Ph.D., student and registrar, Centre for Reproductive Medicine, Academic Medical Centre, Amsterdam, The Netherlands; Roger Lobo, M.D., professor, obstetrics and gynecology, Columbia University and president-elect, American Society of Reproductive Medicine; Peter McGovern, M.D., director, Division of Reproductive Endocrinology and Infertility, Hackensack University Medical Center, professor and director, Division of Reproductive Endocrinology and Infertility, University of Medicine and Dentistry of New Jersey, and medical director, University Reproductive Associates, Hasbrouck Heights, New Jersey; Oct. 30, 2009, BMJ, online

Copyright © 2009 ScoutNews, LLC. All rights reserved.