Background of the study:

Milder stimulation protocols have the advantage of being less expensive and more patient-friendly. Moreover, recent evidence suggests that mild stimulation protocols lead to lower embryo aneuploidy rates compared to conventional treatment regimens. Although with mild stimulation protocols the expected number of oocytes retrieved will be lower, pregnancy rates have shown to be similar possibly because embryo quality outfavours embryo quantity.

Objective of the study:

The aim of the study is to determine whether cycle day (CD) 5 start of stimulation will lead to better quality of embryos, based on morphology, than CD 2 start, in IVF with GnRH antagonist co-treatment started on a fixed day.

Study design:

Prospective randomized trial comparing two different starting days of ovarium stimulation (day 2 versus day 5) for IVF treatment.

Intervention:

One group wil start on cycle day 2 with stimulation of the ovaries with recombinant FSH. The other group will start on cycle day 5. Both group will start suppressing the gonadotrophin production of the the pituitary gland on cycle day 6 with a GnRH antagonist.

Primary study parameters/outcome of the study:

Primary outcome parameter is number of top embryos per ovum pick up.

Secondary study parameters/outcome of the study:

Secondary outcome measures are duration of stimulation, cancellation rate, fertilization rate, number of cumulus oocyte complexes obtained, number of mature oocytes obtained, number of top embryos per started cycle, amount of IU recFSH, and clinical pregnancy rate.