The study investigates if, among women with a regular cycle (between 25 and 45 days), the endometrium is better prepared for the transfer of an embryo that was cryopreserved and if the subsequent embryo implantation rate is higher when the cycle is started with daily, small-dose hormonal injections than in cycles without these daily injections.

Inclusion Criteria:

• Signed informed consent.
• Women with a regular cycle (between 21 and 35 days).
• Embryos with 50% intact blastomeres after thawing.
• Embryo and endometrium are synchronized.

Exclusion Criteria:

• Embryo storage time not longer than 5 years.