Natural conception : Repeated predictions overtime

STUDY QUESTION: How can we predict chances of natural conception at various time points in couples diagnosed with unexplained subfertility? SUMMARY ANSWER: We developed a dynamic prediction model that can make repeated predictions over time for couples with unexplained subfertility that underwent a fertility workup at a fertility clinic. WHAT IS KNOWN ALREADY: The most frequently used prediction model for natural conception (the 'Hunault model') estimates the probability of natural conception only once per couple, that is, after completion of the fertility workup. This model cannot be used for a second or third time for couples who wish to know their renewed chances after a certain period of expectant management. STUDY DESIGN, SIZE, DURATION: A prospective cohort studyingthe long-term follow-up of subfertile couples included in 38 centres in the Netherlands between January 2002 and February 2004. Couples with bilateral tubal occlusion, anovulation or a total motile sperm count