THURSDAY, Aug. 5 (HealthDay News) -- Women who get pregnant within six months after having a miscarriage stand the best chance of having a healthy pregnancy with the fewest complications, Scottish researchers report.

The time that couples should wait after a miscarriage before trying to get pregnant is a matter of debate among medical experts. Some doctors say there is no reason for asking women to hold off trying to conceive, but according to the study authors, the World Health Organization (WHO) recommends waiting at least six months.

The Scottish researchers said their findings suggests the WHO guidelines need to be revisited.

"Our data showed, that at least in Scottish women, there is no justification in delaying a pregnancy following an uncomplicated miscarriage," said lead researcher Dr. Sohinee Bhattacharya, a lecturer in obstetric epidemiology at the University of Aberdeen, Dugald Baird Centre for Research on Women's Health at Aberdeen Maternity Hospital in Aberdeen.

"This research will help health-care providers to counsel women regarding timing of future pregnancies and will allow couples to make informed choices based on hard evidence," Bhattacharya said.

WHO guidelines may still be applicable to women in developing countries, she added.

The report is published in the Aug. 5 online edition of the British Medical Journal.

For the study, Bhattacharya's team collected data on 30,937 women who had had miscarriages in their first pregnancy and then became pregnant again. These women were seen in Scottish hospitals between 1981 and 2000.

The researchers found that women who got pregnant again within six months were less likely to miscarry again, to have to terminate the pregnancy or to have an ectopic pregnancy compared with women who got pregnant six to 12 months after their miscarriage. (They were, however, at a higher risk of induced labor.)

These women were also less likely to have a cesarean delivery, have a premature delivery or have a low birth weight baby, the researchers noted. This association was not due to social and personal factors or by other problems in pregnancy including smoking, they added.

And delaying getting pregnant after a miscarriage carries some risks, they said.

Putting off pregnancy, particularly in developed countries, can be problematic, researchers noted. "Women over 35 are more likely to experience difficulties in conceiving, and women aged 40 years have a 30 percent chance of miscarriage, which rises to 50 percent in those aged 45 years or more. Any delay in attempting conception could further decrease their chance of a healthy baby," they wrote.

Julia Shelley, an associate professor from the School of Health and Social Development at Deakin University in Melbourne, Australia, and author of an accompanying journal editorial, said the study did not conclusively answer the question of when the best time was to get pregnant after a miscarriage.

"In research such as this study, it is not possible to tell whether the intervals between pregnancies were deliberately chosen, or were accidental or involuntary," Shelley said. "Consequently, we cannot really tell whether pregnancies conceived very soon after a miscarriage really do have better outcomes, or whether women [and couples] who conceive quickly following a miscarriage have better outcomes in a subsequent pregnancy than couples who take longer to conceive."

"I think we can say that the study suggests that there is no harm in conceiving again immediately following a miscarriage," Shelley said.

But, she added, "I don't think the study provides good evidence that pregnancies conceived six to 12 months following a miscarriage will have poorer outcomes than those conceived more quickly. For example, the higher rate of pregnancy terminations in pregnancies conceived between 6 and 12 months may mean that more of these pregnancies are unintended."

Another expert, however, suggested the study presents new evidence for trying again sooner following a miscarriage.

"I agree women should wait a couple of months after a miscarriage then try again, but we really never had the hard evidence why we do that," said Dr. George Attia, an associate professor of obstetrics and gynecology at University of Miami Miller School of Medicine.

"It's good to find a study that supports our way of thinking," he said.

More information

For more information on pregnancy, visit the U.S. National Institutes of Health.