The purpose of this study is to comprehensively evaluate the transcriptomic signal of the endometrium before, during, and after the window of receptivity.

Phase 1 will aim to define a normal endometrial transcriptomic signature in healthy controls without infertility. Phase 2 will elucidate endometrial transcriptomic expression in patients with diagnoses of infertility unrelated to endometrial factor. Findings from this phase will be compared to the results of phase 1.

Phase 1:

Major Inclusion: The following are major inclusion criteria:

1. Regular menstrual cycles
2. Age 18-50
3. Normal baseline ultrasound
4. No intrauterine procedures in prior 90 days

Exclusions: The following are exclusion criteria:

1. Any contraindications to undergoing estrogen stimulation of the endometrium

   1. Current smoking status
   2. Multiple risk factors for arterial cardiovascular disease (smoking, diabetes, and hypertension)
   3. Hypertension (systolic ≥140 mmHg or diastolic ≥90 mmHg)
   4. Venous thromboembolism (current or history of)
   5. Known thrombogenic mutations
   6. Known ischemic heart disease
   7. History of stroke
   8. Complicated valvular heart disease (pulmonary hypertension, risk for atrial fibrillation, history of subacute bacterial endocarditis)
   9. Systemic lupus erythematosus (positive or unknown antiphospholipid antibodies)
   10. Migraine with aura at any age
   11. Breast cancer
   12. Cirrhosis
   13. Hepatocellular adenoma or malignant hepatoma

2. History of infertility diagnosis

3. History of undiagnosed abnormal uterine bleeding.

4. Allergic reaction to any medication used for the preparatory cycle

5. Known pregnancy or delivery within the past 6 months

6. Breastfeeding

7. Obesity >35 kg/m2

Phase 2

Major Inclusion: The following are major inclusion criteria:

1. Age 18-50
2. Diagnosis of infertility with low endometrial risk
3. No intrauterine procedures in prior 90 days

Exclusions: In addition to the exclusion criteria for phase 1, patients deemed to have an elevated endometrial risk will also be excluded. This would include the following:

1. Recurrent implantation failure
2. Failed transfer with a euploid blastocyst
3. History of Asherman's or abnormal endometrial function
4. History of endometriosis

Phase 1:

Healthy volunteers without a history of infertility will be recruited for the first phase to undergo an endometrial biopsy on a randomized cycle day surrounding the window of implantation

Phase 2:

Healthy volunteers with a history of infertility but without concern for endometrial dysfunction will be recruited for the second phase to undergo an endometrial biopsy during a preparatory IVF cycle.