There have been two very common forms of progesterone administration that have been used during ovulation induction, in vitro fertilization (IVF) and embryo transfers. There are currently no randomized clinical trials to demonstrate which method of progesterone administration is more effective for frozen embryo transfer. We raise the question: Is there a difference between the two accepted methods of progesterone administration, intramuscular and vaginal suppositories, for frozen embryo transfer? Studies for fresh embryo transfer after in vitro fertilization, have demonstrated that there is not a difference between the two methods of progesterone administration. We will evaluate the question for frozen embryo transfer.

Inclusion Criteria:

• Females < 50 years of age
• Having frozen embryo transfer at Mayo Clinic
• Embryos have been created prior to age 42
• Willing to be randomized to either method of progesterone administration

Exclusion Criteria:

• Diagnosis of severe medical illness
• Uterine lesions affecting the cavity or endometrium
• Uterine anomaly
• Presence of hydrosalpinx
• Extreme difficulty with embryo transfer

Women having a frozen embryo transfer.