The participants will receive metformin 500mg 3times per day for 3months and one month is left for spontaneous pregnancy to occur or not (primary outcome ) and the investigators will check endometrial thickness and subendometerial vascularity as markers of endometrial receptivity before and after the treatment.

Inclusion Criteria:

• PCO syndrome patients have the following criteria:

Age of the patient between 20 - 40 years old. All subjects are not on a specific diet nor a certain program of physical exercise Complaining of infertility either primary or secondary due to PCOS.

N.B: The diagnosis of PCO syndrome was made according to the Androgen Excess and Polycystic Ovarian Syndrome Society: the presence of the following criteria have been required for the diagnosis of PCO syndrome:

Hyperandrogenism: Hirsutism and/or Hyperandrogenaemia Ovarian Dysfunction : Oligo-Anovulation and /or Polycystic ovaries Exclusion of other Androgen Excess or related disorders as :( deficient nonclassic adrenal hyperplasia, androgen-secreting neoplasms, androgenic/anabolic drug use or abuse, Cushing's syndrome, the Hyperandrogenic-Insulin Resistance-Acanthosis Nigricans syndrome, thyroid dysfunction, and hyperprolactinemia).

Exclusion Criteria:

• Age below 20 or above 40. Women who intended to start a diet or a specific program of physical activity. Concurrent medical illness as cardiovascular, neoplastic and hepatic disorder. Pelvic pathology. Tubal, Uterine, Male factor of infertility. Endocrinological factors including: diabetes Mellitus,hypothyroidism, hyperprolactinaemia, Cushing's syndrome, and non- classical congenital adrenal hyperplasia.

Patients who are ovulatory during the ovarian cycle