On the road to single embryo transfer

Abstract

To assess the feasibility of transitioning from day 3 embryo transfers to day 5 single blastocyst transfers. 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. 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. 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. TableElective Single Embryo TransfersDataRangeNumber of Patients33Mean Age of Patient3225–39Mean Eggs Retrieved24.416–42Mean # of 8 cells on D36.51–15Blast. Formation (% of 2 pn's)49.4%15.0–78.6%% of Patients with Blast. Cryo.100%Preg. Rate/Transfer75.8%OG/Preg. Rate/Transfer69.7%Imp. Rate75.8% Open table in a new tab 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.