Selective Single Embryo Transfers: A Preliminary Study L. Keith Smith, Ellen H. Roots and M. Janelle Odom Dorsett The Centre for Reproductive Medicine, Lubbock TX Introduction The culture of human embryos to the blastocyst stage in vitro has been an important advancement in ART, resulting in increased implantation rates and a reduction in the number of embryos transferred in IVF-ET cases (1,2). While higher-order multiple pregnancy rates have been significantly reduced by routinely transferring only 2 blastocysts, the twinning rate still remains abnormally high (3). Twinning increases the risk of pregnancy complications for both the mother and the babies. Twin pregnancies have significantly higher rates of spontaneous abortions, premature births and birth defects. Our ART laboratory has begun to routinely perform selective single embryo transfers if the patient consents and presents at least 1 normal expanded blastocyst with a visible inner cell mass (ICM) (  4AA) on Day 5. Objective Compare the effects of transferring 2 vs 1 embryo(s) on pregnancy, implantation and multiple pregnancy rates in IVF-ET cases with  1 high-grade expanded blastocyst on Day 5. Design An one-year retrospective analysis of all IVF-ET cases with  1 high-grade expanded blastocyst on Day 5 from August 1, 2003 to July 31, Materials/Methods Oocyte insemination was performed with 200,000 motile sperm/mL for 18 hrs in 5-well culture dishes with 500  L of G1.3 media (Vitrolife) + 5% HSA (Vitrolife) overlaid with NidOil (Nidacon) at a density of 1-5 oocytes/well. All 2PN embryos were then cultured in 20  L drops of G1.3 media + 5% HSA overlaid with NidOil for 48 hrs. On Day 3, all viable embryos were transferred to 20  L drops of G2.3 media + 5% HSA overlaid with NidOil and cultured to Day 5 or Day 6. All embryos were cultured at a density of 3-5 embryos/drop in a 37°C incubator with 6% CO 2. Embryo transfers were performed on Day 5 if  1 expanded blastocyst with a visible ICM (  4AA) was present. The decision to transfer 2 or 1 embryo(s) on Day 5 was made in consultation with the physician and patient. Embryo transfers were performed with an 18 cm Wallace embryo transfer catheter containing  15  L of Embryo Glue (Vitrolife). All other transfers were performed on Day 6. Cryopreservation was performed on all expanded blastocysts with a visible ICM (  4BB) on Day 5 and/or Day 6. Serum  hCG tests were performed at 10 days post-transfer. Fetal cardiac activity was determined by transvaginal ultrasound at 5 weeks post-transfer. The implantation rate was defined as the number of fetal heartbeats/number of embryos transferred. Multiple pregnancies were defined as > 1 fetal heartbeat on ultrasound at 5 weeks post-transfer. Donor oocytes were utilized in 5% and ICSI in 10% of the IVF-ET cases. Statistical analysis was performed using either Chi square or Student’s t-test. Results Table 1: Analysis of the IVF-ET Cases. Number Transferred on Day 5 2 Blastocysts1 Blastocyst Transfers4520 Patients’ Age32.0 ± ± 2.8 Prior IVF Cycles0.4 ± ± 0.5 Oocytes Retrieved15.2 ± ± 8.2 % Fertilization (2PN)70.0%70.7% % Cleavage95.8%97.8% % Blastulation65.4%63.2% % of Embryos Cryopreserved25.4%31.1% Results are expressed as the mean ± one standard deviation or as a % of the total oocytes or 2PN embryos. Results were compared using either Chi square or Student’s t-test. Table 2: Pregnancy and Implantation Rates Following Double Embryo vs Selective Single Embryo Transfers Number Transferred on Day 5 2 Blastocysts1 Blastocyst % Positive  hCG84.4% (38/45)90.0% (18/20) % Fetal Cardiac Activity80.0% (36/45)80.0% (16/20) % Live Births/ Ongoing Pregnancies73.3% (33/45)70.0% (14/20) % Implantation63.3% (57/90)90.0% (18/20) a % Multiple Pregnancies58.3% (21/36)12.5% (2/16) b All pregnancy rates are expressed/transfer. Results differ from 2 blastocysts at a p < and b p < Chi square. Discussion In IVF-ET cases that present  1 high-grade expanded blastocyst (  4AA) on Day 5, reducing the number of blastocysts transferred from 2 to 1 had no significant effects on pregnancy or live birth rates. However, reducing the number of embryos transferred from 2 to 1 does significantly increase the implantation rate and dramatically reduces the multiple pregnancy rate. These results demonstrate that selective single embryo transfers coupled with blastocyst culture can dramatically reduce the rate of multiple pregnancies without significantly altering pregnancy or live birth rates in IVF-ET cases with  1 high-grade expanded blastocyst (  4AA) on Day 5. Conclusions Selective single embryo transfers produce similar pregnancy rates compared to double embryo transfers, while significantly reducing the multiple pregnancy rate in IVF-ET cases with  1 high-grade expanded blastocyst on Day 5. References 1. Gardner DK, Vella P, Lane M, Wagley L, Schlenker T, Stevens J, Schoolcraft WB. Culture and transfer of human blastocysts increases implantation rates and reduces the need for multiple embryo transfers. Fertil Steril 1998;69: Gardner DK, Schoolcraft WB, Wagley L, Schlenker T, Stevens J, Hesla J. A prospective randomized trial of blastocyst culture and transfer in in-vitro fertilization. Hum Reprod 1998;13: Milki AA, Fisch JD, Behr B. Two-blastocyst transfer has similar pregnancy rates and a decreased multiple gestation rate compared with three-blastocyst transfer. Fertil Steril 1999;72: Pregnancy rates are expressed as ongoing pregnancies or live births/transfers. Multiple pregnancy rates are expressed as the % of clinical pregnancies with > 1 fetal heartbeat. *** Results differ from 2 blastocysts at p < Chi square.