To compare the number of retrieved oocytes in the late start CF-alfa (day 4) versus standard CF-alfa protocols (day 2) in patients undergoing IVF. The primary analysis will be also performed in specific subgroups of patients: expected poor-responders, expected normal responders and expected hyper-responders

The investigators hypothesize that:

1. CF-alfa late start (day 4) will show comparable efficacy in terms of number of retrieved oocytes versus standard CF-alfa (day 2) protocol. In certain groups of patients, CF-alfa late start might show differences in terms of efficacy such as in poor-responder patients.
2. CF-alfa late start (day 4) will obtain similar results in terms of vital pregnancy rates with a similar safety profile with respect to COS performed using CF-alfa standard administration (day 2) in expected normal, poor, or high responders.
3. Oocytes and embryos obtained using CF-alfa late start will have comparable morphological features and development potential than those obtained with CF-alfa standard.
4. The patients' satisfaction will possibly be higher using CF-alfa late start than with CF-alfa standard expecially in those patients who will not have the need to add further daily recFSH injections

Inclusion Criteria:

• aged 18- 43 years
• Male or tubal infertility with indication for IVF treatment
• No PCOS
• No previous IVF treatments in the past two months
• No history of previous Ovarian Hyperstimulation Syndrome (OHSS)
• No previous IVF cycle with more than 30 growing follicles ≥ 11 mm
• Antral Follicle Count (AFC) <20
• No ovarian cyst nor malignant ovarian tumour, breast, uterus or central nervous cancer

Exclusion Criteria:

• AMH < 0.2 ng/ml
• Età > 43 anni