Cryo-thawed embryo transfer: natural versus artificial cycle. A non inferiority trial.

Cryopreservation of embryos derived from IVF or IVF-ICSI treatment is a save
and cost efficient supplement to regular IVF treatment. Before transferring the
embryo*s into the uterus it*s necessary to synchronise development of embryo
and endometrium. This synchronisation is essential for the success of the
treatment. Because of this need cryo embryo transfer needs planning en
preparation. The are several methods of endometrial preparation preceding
frozen thawed embryo transfer. Most common are natural cycle and artificial
cycle preparation. Both are accepted methods of endometrium preparation and
it*s common opinion that live birth rates are comparable. Despite this claim so
far no randomised study has been undertaken to confirm this statement.

To compare live birth rates among patients receiving cryo thawed embryo
transfer after endometrial preparation with estrogen/progesterone substitution
and patients receiving cryo thawed embryo transfer in a natural cycle.

Non inferiority, randomized trial.

Due to the fact that both preparation methods are well accepted there*s no
obvious intervention. The investigational team had decided to choose for
intervention 1 (natural cycle) and intervention 2
(artificial cycle). Subjects assigned to intervention 1 will receive several
trans vaginal ultrasonic measurements combined with subcutaneous HCG injection
proceeding embryo transfer. Subjects assigned to intervention 2 are prepared
for embryo transfer by medication. (oral estrogens and progesterone per
vaginam)

Patients will participate in this study during 1 treatment cycle (1 embryo
transfer of a frozen thawed embryo). There are little risks in both methods of
endometrium preparation. Possible risks for patients assigned to the artificial
cycle are side effects of medication and a 2 times higher risk of a
trombo-embolic event. Because both methods of preparation are well accepted and
used in the Netherland the investigational team accepts these risk as being
minor. No extra examinations or taking of blood samples will be performed.

Patients are asked to fill out several questionnaires in order to retrieve
information about cost, side effects, burden and stress perceived during
treatment and to follow up pregnancy outcomes. Filling out these forms will
take place at two occasions and will take respectively 30 and 10 minutes.