Exogenous control of the cycle simplifies thawed embryo transfer and results in a pregnancy rate similar to that for natural cycles.

To determine if a satisfactory PR could be achieved in thawed ET using a simplified protocol, standard monitoring in the natural cycle was compared with a controlled preparation of the endometrium with exogenous E2 and P without hormonal or ultrasonographic monitoring. All patients had normal ovarian function, and no GnRH-a were administered. Pregnancy rates, ongoing PRs, and embryo implantation rates were similar in the two groups. The use of exogenous E2 and P without GnRH-a suppression to control the cycle for thaw ET is safe, convenient, and results in PRs at least as good as in the natural cycle. It may be of particular value in patients with an irregular cycle or in those for whom prolonged monitoring is undesirable.