The purpose of this study is to compare pregnancy outcomes of frozen-thawed embryo transfer after endometrial preparation with vaginal estradiol or transdermal estradiol and to evaluate women's satisfaction

Frozen-thawed transfer embryo are more and more frequent but to date, there is no consensus on the ideal management of the adequate endometrial preparation.

Artificial preparation of endometrium is commonly used in assisted reproduction center because it is more easy to schedule.

Estradiol could be administrate by oral, vaginal or transdermal, but no protocol seems to improve clinical pregnancy rates.

To investigator's knowledge, transdermal estradiol has never been compare to vaginal administration before frozen-thawed embryo transfer.

Because transdermal administration could improve satisfaction of patients and reduce duration of treatment (when compare to oral administration), the investigators conduct a prospective study to compare clinical pregnancy rate after transdermal or vaginal estradiol administration to prepare the endometrium before frozen-thawed embryo transfer.

The investigator also evaluate side effects and patients satisfaction in both protocol.

The patients choose if they prefer vaginal or transdermal protocol after receiving sufficient information during medical consultation.

Inclusion Criteria:

• age ≥ 18 and <43
• frozen-thawed embryo transfer after exogenously administered estrogen in either way transdermal or vaginal
• patients who accepted being included and signed the consent forms.

Exclusion Criteria:

• patient who refuse to participate
• frozen-thawed embryotransfer after stimulated or natural cycle
• oocyte or sperm donation
• endometrial thickness after 21 days <6mm
• non-french speaking patients
• women under legal guardianship
• women with no health or social security coverage

female

patients follow in our assisted reprodution unit, requesting frozen-thawed embryo transfer after ivf or icsi