Frozen-thawed embryo transfer (cryo-embryo transfer) in the natural cycle of a woman is based on the timing of the ovulation. There are two methods to monitor the ovulation: (1) home-based monitoring in which the natural ovulation is monitored using urinary LH tests ; and (2) hospital-based monitoring using repeated ultrasound monitoring of the dominant follicle followed by human chorionic gonadotropin (hCG) triggering for ovulation. The Antarctica-2 RCT compares the (cost-) effectiveness and womens' preference of home-based monitoring with hospital-based monitoring of the ovulation.