Effects of Varied Estrogen Doses on Endometrial Receptivity

Inclusion Criteria: * Regular menstrual cycles * Age 18-50 * Normal Baseline ultrasound * No intra-uterine procedures in prior 90 days Exclusion Criteria: * Any contraindications to undergoing estrogen stimulation of the endometrium * Age ≥35 years and smoking ≥15 cigarettes per day * Multiple risk factors for arterial cardiovascular disease (smoking, diabetes, and hypertension) * Hypertension (systolic ≥140 mmHg or diastolic ≥90 mmHg) * Venous thromboembolism (current or history of) * Known thrombogenic mutations * Known ischemic heart disease * History of stroke * Complicated valvular heart disease (pulmonary hypertension, risk for atrial fibrillation, history of subacute bacterial endocarditis) * Systemic lupus erythematosus (positive or unknown antiphospholipid antibodies) * Migraine with aura at any age * Breast cancer * Cirrhosis * Hepatocellular adenoma or malignant hepatoma * History of undiagnosed abnormal uterine bleeding. * Allergic reaction to any study drug * Known pregnancy or delivery within the past 6 months * Breastfeeding * Obesity \>35 kg/m2