Comparison of Transfers of Fresh and Thawed Embryos in Normal Responder Patients

• Clinical pregnancy (fetal heartbeat observed on ultrasound at 7 weeks gestation) [ Time Frame: 7 weeks gestation ] [ Designated as safety issue: No ]
  

• Ongoing pregnancy at 10 weeks gestation [ Time Frame: 10 weeks gestation ] [ Designated as safety issue: No ]
  
• Implantation rate (ratio of the number of fetal heart tones to the number of transferred blastocysts) [ Time Frame: 7 weeks gestation ] [ Designated as safety issue: No ]
  

The purpose of this study is to determine if blastocyst transfers in cycles of post-thaw extended culture (PTEC) have different efficacy than transfers of fresh blastocysts in patients with expected normal response to ovarian stimulation.

Multiple studies have found altered endometrial histology and gene expression following controlled ovarian stimulation.

PTEC cycles require cryopreservation of the entire 2pn oocyte cohort in the prior cycle. Once thawed, the embryos are cultured to the blastocyst stage before transfer.

In typical cycles using frozen-thawed embryos, many thawed embryos that appear to survive do not actually resume and continue development. PTEC ensures the transfer of embryos that resumed development and continued developing at least to the blastocyst stage (4-5 days post-thaw).

The viability of a blastocyst in a PTEC cycle has been shown to be on par with that of a fresh blastocyst. Therefore, comparing outcomes of blastocyst transfers in PTEC cycles with that in fresh autologous cycles allows the potential endometrial impact of controlled ovarian stimulation to be assessed.