The purpose of this study is to compare efficacy and tolerability of the dydrogesterone and the vaginal progesterone, used for luteal phase support.

(Initial start date was January 2009 but not for patients' recruitment only for paper work, documents, team organization, statistical pre-work actions and to gain the official approval of Institutional Review Board. The recruitment started in October 2010 and continued until October 2013.)

The use of gonadotropin-releasing hormone (GnRH) agonists in the ovarian stimulation, which prevents a premature surge of luteal hormone (LH), ultimately leads to suppression of the pituitary gland and high levels of estrogen observed during induced cycles result in inhibiting effect on the implantation of human embryos.

The luteal support in in-vitro-fertilization (IVF) cycles can be prolonged using human chorion gonadotropin(hCG) and/or progesterone.

Since it has been noted that the use of hCG was related with higher risks of the onset of ovarian hyperstimulation syndrome (OHSS), progesterone is nowadays a product of choice in luteal support.

Currently vaginal progesterone is widely used, since the classic oral progesterone results in low bioavailability and lower pregnancy rate and the intramuscular progesterone (IM-P) daily injections are painful and may cause abscesses, inflammatory reactions and local soreness.

However, standard protocol for luteal phase support has not been established (i.e. optimal dosage, route or duration).

Dydrogesterone is a retroprogesterone with good oral bioavailability. Oral administration is clear advantage, due to expected higher patient compliance and better tolerability than currently used vaginal or IM-P.

We hypothesize that dydrogesterone has the same efficacy as vaginal progesterone but better tolerability due to less side effects.

Inclusion Criteria:

• routine ovulation induction protocol with GnRH agonist
• less than three prior IVF cycles
• at least three aspirated oocytes
• BMI <35 kg/m2
• age <45 years

Exclusion Criteria:

• history of dysfunctional uterine bleeding
• acute urogenital disease
• recurrent miscarriage
• previous allergic reactions to a progesterone products