Women who experience two or even more unexplained miscarriages are still likely to conceive and carry a child, with about 65% giving birth to a live infant, results of two new studies show.
Most of the successful pregnancies seem to occur within a year or so after a woman sees a fertility specialist, Dr. Ole Christiansen said during a press briefing at the annual meeting of the European Society of Reproduction and Embryology. Success is not related to treatment, since none exists for unexplained miscarriage. Instead, said Dr. Christiansen of Rigshospitalet, Copenhagen, the declining incidence of birth over 5 years is probably related to increasing maternal age with each attempt, or to the decision to give up efforts to conceive.
Dr. Stef P. Kaandorp
Dr. Stef P. Kaandorp, whose study came to a similar conclusion, said the results of both are encouraging.
"Women with recurrent miscarriage can be reassured that their time to a subsequent conception is not significantly longer that that for fertile women without a history of miscarriage," said Dr. Kaandorp, a research fellow at the University of Amsterdam. "Recurrent miscarriage is extremely stressful for these women, and we hope that our study will give them hope and encourage them to keep trying for the baby they want so much."
Prof. Christiansen presented a population-based retrospective study conducted in Denmark. Data were extracted from the National Danish Birth registry and identified 987 women who had at least three consecutive miscarriages and had been referred to a specialist clinic between 1986 and 2008. All of these women were aged 20-46 years at the time of referral. About one-third had some prior fertility treatments, including hormones, anticoagulants, and intravenous immunoglobulin.
Overall, 66% of the women (651) achieved a live birth after the consultation, Dr. Christiansen said. The highest rate occurred within the first 15 months of the consultation (71%). "The curve declines very rapidly after the first year after the consultation, then after 5 years it really flattens out," he said. "Only 2%-3% are likely to have a child after that."
Subgroup analyses found that increasing maternal age and the number of prior miscarriages were significantly associated with a continued rate of unsuccessful pregnancy. Nor were prior infertility treatments related to a later live birth, he said.
However, the new data should allow researchers to create a risk estimate graph that can predict the chance of a live birth much more precisely. "Instead of giving these women an uncertain risk estimate [for future live birth], we can now combine their age and number of miscarriages to give them a closer estimate of a live birth, and that is what matters to these women," he said.
Future research on this same cohort may look at what factors the male partner brings to the picture of recurrent miscarriage – if any.
In the second study, Dr. Kaandorp conducted a subanalysis of the ALIFE trial – a randomized, placebo-controlled study that showed neither aspirin combined with nadroparin nor aspirin alone improved the live-birth rate among women with unexplained recurrent miscarriage; the study ran from 2004-2008 (N. Engl. J. Med. 2010;362:1586-96).
Of the 364 women enrolled in that trial, Dr. Kaandorp identified 251 who had at least two miscarriages with a gestational age of 20 weeks or less and examined their subsequent rates of conception and live birth.
Of the cohort, 213 became naturally pregnant during by 2009. The median time to conception, regardless of outcome, was 21 weeks, although the range was 8-55 weeks. The cumulative pregnancy rate was 56% after 6 months, 74% after 12 months, and 86% after 24 months.
Of those who did conceive, 139 gave birth to a living child; 69 experienced another miscarriage; 2 had an ectopic pregnancy; 2 terminated the pregnancy; and 1 had an intrauterine death.
The presence of the Factor V Leiden genetic condition was the only factor significantly related to a shorter time to pregnancy; it increased by 91% the chance of conception by 11 weeks, compared with noncarriers.
"We should be cautious with this finding, because it only occurred in 11 women," Dr. Kaandorp noted. "At this point, I think we can only see it as hypothesis generating."
Neither Dr. Christiansen nor Dr. Kaandorp had any financial disclosures.