Women who try again soon after a miscarriage may be more successful and fare better than those who delay trying to conceive, researchers found.
In a population-based study, women who conceived within six months of their initial miscarriage were 34 percent less likely to miscarry a second time compared with those who got pregnant again six to 12 months afterwards.
A short interval between pregnancies also was linked to lower risk of ectopic pregnancy and cesarean or preterm delivery for these women, Sohinee Bhattacharya of Aberdeen Maternity Hospital in Aberdeen, Scotland, and colleagues reported online in BMJ.
"Women wanting to become pregnant soon after a miscarriage should not be discouraged," they wrote in the paper.
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How soon to try again is the number one question for women actively seeking to become pregnant, but one that has a remarkable lack of evidence, according to an accompanying editorial.
Julia Shelley of Deakin University in Burwood, Australia, called the findings surprising and cautioned that selection and measurement bias may have been at play.
"Of greatest concern is that women with short interpregnancy intervals are more fertile than those whose subsequent pregnancy occurs later because these women seem to have better pregnancy outcomes and fewer complications," Shelley wrote in the editorial.
World Health Organization guidelines recommend waiting at least six months before trying to become pregnant after miscarriage.
Indeed, mental recovery may take some time, and delay may be desirable if there are signs of infection, Bhattacharya's group acknowledged.
But a delay poses problems for women in the Western world, where for social and economic reasons women tend to delay childbearing, they noted.
For these women, "any delay in attempting conception could further decrease the chances of a healthy baby," Bhattacharya and colleagues wrote in the paper.
The group analyzed records for all 30,937 women who had a miscarriage in their first recorded pregnancy and subsequently became pregnant as recorded in Scottish national databases between 1981 and 2000.
The largest proportion (41.2 percent) of the women conceived within six months of their miscarriage, while the interval was six to 12 months for another 25.2 percent, 12 to 18 months for 9.6 percent, 18 to 24 months for 6.4 percent, and even longer for 17.6 percent.
The live birth rate dropped from 85.2 percent in women who got pregnant again within six months down to 73.3 percent in those with an interval of more than 24 months.
The trend was similar for termination of pregnancy, which was 57 percent less likely with an interval of less than six months between miscarriage and subsequent pregnancy compared with an interval of six to 12 months.
Other outcomes largely followed the same pattern for a less than six month versus six to 12 month interval. The only exception was that getting pregnant less than six months after a miscarriage was associated with higher risk of induced labor than an interval of six to 12 months.
The highest risks came with an interpregnancy interval of more than 24 months, which was associated with 97 percent increased risk of ectopic pregnancy and 2.40-fold risk of termination.
Other significant risks associated with a more than 24-month interval were preterm, very preterm, and cesarean delivery as well as a low birthweight infant.
The researchers cautioned that the study may have been limited by potential misclassification and the possibility that the miscarriage recorded may not have been a first event. They also noted that the Scottish population is fairly homogeneous, which could limit generalizability.