Progestin-induced Endometrial Shedding in PCOS (The PIES in PCOS Study)

Inclusion * Women aged 18 - 40, desiring pregnancy * Established diagnosis of PCOS confirmed by the Rotterdam criteria * Oligo or anovulatory, with menstrual cycles \> 35 days apart or less than 9 menstrual cycles per year * Normal vaginal ultrasound with endometrial stripe \< 12 mm * Normal thyroid stimulating hormone (TSH) within past one year * Normal prolactin (PRL) within past one year * For women with previous successful Clomid treatment, a washout period of at least 2 months is required Exclusion * Regular menstrual cycles occurring less than 35 days apart * Evidence of other infertility factors such as endometriosis, tubal factor or male infertility * Prior unsuccessful Clomiphene citrate ovulation cycles * Abnormal vaginal ultrasound findings such as endometrial polyps, submucous myomas, synechiae * Uterine anomaly such as unicornuate or bicornuate uterus * Presence of hydrosalpinx * Evidence of active endocrinopathy, such as thyroid disorder or hyperprolactinemia * Partner with abnormal semen analysis (count \< 15 million sperm /ml)