Multi-center, parallel-group, randomized controlled trial of modified natural versus programmed cycles for frozen embryo transfers and their association with preeclampsia and live births (NatPro)

The primary objective is to determine the proportion of preeclampsia in pregnant women assigned to a modified natural cycle FET (corpus luteum present) protocol compared to a programmed FET (corpus luteum absent) protocol. The secondary objective is to determine the cumulative proportion of live births in the modified natural cycle FET (corpus luteum present) compared to the programmed FET (corpus luteum absent).