Objective:

To assess the feasibility of transitioning from day three embryo transfers to day five single blastocyst transfers.

Design:

Elective single embryo day 5 transfers (ESET) between January 2006 and March 2007 were retrospectively analyzed. Donor cycles were not included in the study group. Patients were chosen based on good prognosis or on hyperstimulation risk factors.

Materials and Methods:

Oocytes were retrieved in HTF (InVitrocare) or Fertilization Media (Sage-Cooper), hyaluronidased after 2 to 3 hours incubation and ICSI’ed 1 to 3 hours following cumulus-corona removal. Oocytes were placed in IVC-1 (IVC) or Cleavage Media (Sage) after ICSI and cultured individually in this media until Day 3. Embryos were placed into CCM (Vitrolife) or Blastocyst Media (Sage) on the morning of Day 3 for extended culture. The best embryos were identified and laser hatched prior to transfer using the Zilos laser system (Hamilton Thorne). Morphologic assessment occurred on Day 2, 3, 5, 6 and 7. Spare embryos developing to blastocysts were vitrified for future use.

Results:

Elective Single Embryo Transfers

	Data	Range
Number of Transfers	33
Mean Age of Patient	32	25–39
Mean Eggs Retrieved	24.4	16–42
Mean # of 8 cells on Day 3	6.5	1–15
Blast Formation as % of Total 2PN’s	49.4	15.0–78.6
% of Patients with Blasts Cryopreserved	100%
Pregnancy Rate/Transfer	75.8
Ongoing Pregnancy Rate	69.7
Implantation Rate	75.8

The mean age, mean eggs retrieved and 2PN blast formation were 32, 24.4 and 49.4% respectively for the study group. Of the 33 transfers analyzed, 25 patients achieved pregnancy with 23 pregnancies ongoing, yielding a 69.7% ongoing pregnancy rate. All patients in this group had blasts vitrified for subsequent use.

Conclusions:

This data is meant to be used by others contemplating ESET in their clinics. ESET has conferred a number of beneficial aspects to our practice. For example, the application of less subjective embryo/blastocyst grading has resulted in better selection for transfer. Also, the additional two days provides our clinical staff with more time to assess Ovarian Hyperstimulation Syndrome risk - transfer on day 5 becomes clearly advisable or inadvisable if clinical symptoms do not resolve. The future challenge will be application of ESET more liberally and across a broader patient population.