Time to conception and time to live birth in women with unexplained recurrent miscarriage.

STUDY QUESTION: What is the time to conception in a cohort of women with unexplained recurrent miscarriage (RM). SUMMARY ANSWER: Median time to conception in women diagnosed with unexplained RM was 21 weeks (interquartile range (IQR) 8-55 weeks), with a cumulative incidence of conception of 74% after 12 months of trying to conceive. WHAT IS KNOWN ALREADY: There is no effective treatment in couples with unexplained RM. Adequate counselling about their prognosis, for example time to conception and time to a live birth, is therefore very important. So far, there are no studies that give insight on these issues. STUDY DESIGN, SIZE, DURATION: A nested prospective cohort study was performed from February 2004 through July 2009 within a multicentre randomized placebo-controlled trial (ALIFE trial) on anticoagulant treatment in 364 women with unexplained RM. PARTICIPANTS/MATERIALS, SETTING, METHODS: A total of 251 women who were not pregnant at the time of diagnosis of unexplained RM were included in this study. Of these, 13% became pregnant with ART, and all other women conceived naturally. The primary outcome was time to conception in weeks, calculated from the moment of diagnosis until conception measured by a urinary HCG. Secondary outcome was time to a live birth in the subsequent pregnancy. The relative prognostic significance of female age, the number of preceding miscarriages, interventions within the trial and the presence or absence of a preceding late miscarriage, a previous live birth and factor V Leiden mutation, was evaluated by Cox regression for time to conception and by competing risk modelling for time to live birth, respectively. MAIN RESULTS AND THE ROLE OF CHANCE: The cumulative incidence of conception was 56% after 6 months, 74% after 12 months and 86% after 24 months of which 65% resulted in a live birth. The median time to conception was 21 weeks (IQR 8-55 weeks). Of potential prognostic factors, the presence of the factor V Leiden mutation resulted in a significantly shorter median time to conception of 11 weeks for carriers versus 23 weeks for non-carriers (hazard ratio (HR) 1.94, 95% confidence interval (CI) 1.03-3.65). The cumulative incidence of a live birth of the subsequent pregnancy was 0% after 6 months, 23% after 12 months and 50% after 24 months. The median time to a live birth of the subsequent pregnancy was 102 weeks (IQR 82-115 weeks). The number of previous miscarriages was the only prognostic factor (HR 0.83, 95% CI 0.74-0.94) significantly associated with time to a live birth of the subsequent pregnancy. LIMITATIONS, REASONS FOR CAUTION: In our study only the subsequent pregnancy after diagnosing unexplained RM was included. A future collection of cumulative follow-up data of all the women included in this cohort may provide outcomes of all pregnancies following the diagnosis of unexplained RM. WIDER IMPLICATIONS OF THE FINDINGS: Time to conception in women diagnosed with unexplained RM appears to be comparable with time to conception in healthy fertile women, as reported in the literature. The interesting finding that women with Factor V Leiden mutation have a significant shorter time to conception may suggest a favourable embryo implantation process. Future research is needed to confirm these findings and unravel the biology of early implantation. STUDY FUNDING/COMPETING INTEREST(S): The RCT used for this nested cohort study was funded by a grant (945-27-003) from the Netherlands Organization for Health Research and Development and a grant from GlaxoSmithKline. Study drugs (aspirin and placebo) were packaged and donated by Meda Pharma. This analysis was supported by a VIDI innovative research grant from the Netherlands Organisation for Scientific Research (NWO) 016.126.364. There are no potential conflicts of interest to declare. TRIAL REGISTRATION NUMBER: This cohort study was nested in the randomized controlled trial; ALIFE study (Current Controlled Trials number, ISRCTN 58496168).