The chances to achieve pregnancy after retrieving >15 oocytes are not good, probably because of bad effect on the endometrium (uterine inner lining). Therefore, in most such cases the investigators prefer to freeze all embryos, and transfer in a thaw cycle. With the introduction of oocyte vitrification (very fast cooling) technology, a new option emerged: to freeze un-fertilized eggs, to be fertilized and used later in a thaw cycle.

The purpose of this study is to compare the outcome of these two approaches.

Inclusion Criteria:

• IVF patients
• ovulation trigger with Decapeptyl 0.2 mg because of ovarian hyper-response: E2 on trigger day .12,000 pmol/l and/or >15 oocytes.
• Normal uterus

Exclusion Criteria:

• <20% fertilization rate