The present study aims to elucidate if there is a metabolomic profile alteration in the embryos of obese women in order to understand if the reduced implantation rate observed in these patients is directly related to this factor. Furthermore, the investigators seek to establish if there is any difference between obese women with Polycystic Ovary Syndrome (PCO) and without PCO. The investigators compare these metabolomic profile embryos with embryos of egg-donation programme.

Inclusion Criteria:

• BMI > 30 kg/m2
• Age < 38 years old
• Non smokers
• First IVF cycle (groups 2 & 3, not Control group)
• Normal uterus (seen by ultrasound)
• normal basal hormonal profile(FSH,LH,estradiol,testosterone,androstenedione, insulin, SHBG, glucose, AMH)
• Antral follicle count(> 5 FA for each ovary)
• Menses every 25-35 days.

Exclusion Criteria:

• < 5 or > 20 oocytes retrieved after stimulation cycle
• estradiol >3000 pg/ml or progesterone > 1,5 ng/ml on the hCG day.
• < 2 evolutive embryos in the culture medium.

45 women divided into three groups: A)15 Obese women without Polycystic Ovarian Syndrome: BMI > 30 kg/m2 , age < 38 years old, normal basal hormonal profile (FSH, LH, estradiol, testosterone, androstenedione, insulin, SHBG, glucose, AMH, and antral follicle count(> 5 FA for each ovary), menses every 25-35 days.

B)15 Obese women with Polycystic Ovarian Syndrome: BMI > 30 kg/m2, age < 38 years old, basal hormonal profile with or without hyperandrogenism and ultrasound ovary aspect of PCO.

C)15 Fertile women (egg-donors): BMI 20-24.9 kg/m2. All the patients have normal uterine conditions, are not smokers, without endometriosis or hidrosalpinx. All the male partners have sperm parameters: count(> 5 mill/ml,15% motility,> 0% normal morphology)and BMI < 28 kg/m2.