Serum progesterone levels prepare the endometrium for implantation and play an important role during embryo transfer (ET). In clinical practice, luteal phase support progesterone supplementation is systematically offered to all women undergoing medically assisted procreation (AMP), independently of ET conditions (fresh and frozen).

The investigators propose to perform a prospective cross-sectional single-center cohort study to measure progesterone levels on the day of the ET on all AMP cycles and to compare these levels between active pregnancies and ET unsuccessful cycles. They will determine progesterone threshold levels corresponding to successful attempts in all ET strategies (fresh and frozen) as well as clinical and biological risk factors leading to luteal phase deficiency during ET. They could therefore individualize progesterone supplementation according to patient's needs.

Inclusion Criteria:

• Age ≥ 18 years
• planned embryo transfer
• signed informed consent

Exclusion Criteria:

• patients falsely included, major inclusion criteria not respected
• lack of social insurance
• refusal to participate in the research

all patients who need an embryo transfer in the center.