This study evaluates the incidence of Non Receptive endometrium in obese infertile women compared to infertile normal weight women using Endometrial Receptivity Array (ERA) test, containing 238 genes, identifying the receptivity status of an endometrial sample and diagnosing the patient's Window of Implantation, regardless of the histological appearance of the sample. An endometrial biopsy is collected from the uterine fundus, either in a natural cycle or in a hormonal replacement therapy (HRT) cycle and the test is performed.

Inclusion Criteria:

• Infertile women: > 1 year of regular unprotected intercourse without evidence of pregnancy.
• Normal uterus by 2D/3D ultrasound scan and/or hysteroscopy
• No endometriosis
• Presence of both ovaries
• < 45 years old (in ovum donation, outcome parameters are not affected until this age in all the current published studies).

Exclusion Criteria:

• Hydrosalpinx
• Stage 3-4 endometriosis diagnosed with ultrasound, laparoscopy/ laparotomy.
• Implantation failure (≥ 4 pre-embryos of good quality transferred without pregnancy)
• Recurrent pregnancy loss (≥ 2 pregnancies biochemical / clinical)