Women who suffer a miscarriage may have the best chance of having a baby if they get pregnant again within six months, new research says.

Doctors in Scotland followed nearly 31,000 women who went to the hospital for a miscarriage in their first pregnancy and subsequently became pregnant between 1981 and 2000.

Among women who got pregnant within six months, 85 percent had a healthy baby. Among women who waited more than two years to get pregnant again, the rate was 73 percent. The study was published today in the medical journal BMJ and was partly funded by the Chief Scientist’s Office in Scotland, an agency of the Scottish government.

“It’s unnecessary for women to wait to conceive again after a miscarriage,’’ said Sohinee Bhattacharya, a lecturer in obstetric epidemiology at the University of Aberdeen in Scotland, one of the paper’s authors.

She said current guidelines from the World Health Organization, which recommend women delay getting pregnant for at least six months after a miscarriage, should be changed. Bhattacharya said WHO guidelines are based on a study from Latin America, where women usually have children at an earlier age.

Because women in developed countries often wait until they are older to have children, Bhattacharya said any delays to conception could reduce the chances of a healthy baby.

Women over 35 are more likely to have problems getting pregnant, and women over 40 have a 30 percent risk of a miscarriage. Normally the miscarriage rate is about 20 percent.

Britain’s Royal College of Obstetricians and Gynaecologists doesn’t advise women to wait a certain amount of time before trying for a baby after a miscarriage.

“If you wish to be pregnant, trying again soon, whenever you feel physically and emotionally ready, does not increase your risk of miscarrying the next time,’’ said Dr. Tony Falconer, the college’s president-elect.