Selective Single Embryo Transfers: A Preliminary StudyL. Keith Smith, Ellen H. Roots and M. Janelle Odom Dorsett

The Centre for Reproductive Medicine, Lubbock TX

IntroductionThe culture of human embryos to the blastocyst stage in vitro hasbeen an important advancement in ART, resulting in increasedimplantation rates and a reduction in the number of embryostransferred in IVF-ET cases (1,2). While higher-order multiplepregnancy rates have been significantly reduced by routinelytransferring only 2 blastocysts, the twinning rate still remainsabnormally high (3). Twinning increases the risk of pregnancycomplications for both the mother and the babies. Twin pregnancies have significantly higher rates of spontaneousabortions, premature births and birth defects.

Our ART laboratory has begun to routinely perform selectivesingle embryo transfers if the patient consents and presents atleast 1 normal expanded blastocyst with a visible inner cell mass(ICM) ( 4AA) on Day 5.

ObjectiveCompare 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.

DesignAn one-year retrospective analysis of all IVF-ET cases with 1high-grade expanded blastocyst on Day 5 from August 1, 2003to July 31, 2004.

Materials/MethodsOocyte insemination was performed with 200,000 motile sperm/mLfor 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 1-5oocytes/well. All 2PN embryos were then cultured in 20 L drops ofG1.3 media + 5% HSA overlaid with NidOil for 48 hrs. On Day 3, allviable 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 embryoswere cultured at a density of 3-5 embryos/drop in a 37°C incubator with6% CO2. Embryo transfers were performed on Day 5 if 1 expandedblastocyst with a visible ICM ( 4AA) was present. The decision totransfer 2 or 1 embryo(s) on Day 5 was made in consultation with thephysician and patient. Embryo transfers were performed with an 18cm Wallace embryo transfer catheter containing 15 L of EmbryoGlue (Vitrolife). All other transfers were performed on Day 6.Cryopreservation was performed on all expanded blastocystswith a visible ICM ( 4BB) on Day 5 and/or Day 6.

Serum hCG tests were performed at 10 days post-transfer. Fetalcardiac activity was determined by transvaginal ultrasound at 5 weekspost-transfer. The implantation rate was defined as the number of fetalheartbeats/number of embryos transferred. Multiple pregnancies weredefined 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 52 Blastocysts 1 Blastocyst

--------------------------------------------------------------------------Transfers 45 20

Patients’ Age 32.0 ± 4.0 31.1 ± 2.8

Prior IVF Cycles 0.4 ± 0.6 0.2 ± 0.5

Oocytes Retrieved 15.2 ± 9.0 15.1 ± 8.2

% Fertilization (2PN) 70.0% 70.7%

% Cleavage 95.8% 97.8%

% Blastulation 65.4% 63.2%

% of Embryos Cryopreserved 25.4% 31.1%

Results are expressed as the mean ± one standard deviationor as a % of the total oocytes or 2PN embryos. Results werecompared using either Chi square or Student’s t-test.

Table 2: Pregnancy and Implantation Rates FollowingDouble Embryo vs Selective Single Embryo Transfers

Number Transferred on Day 52 Blastocysts 1 Blastocyst

-------------------------------------------------------------------------------% Positive hCG 84.4% (38/45) 90.0% (18/20)

% Fetal Cardiac Activity 80.0% (36/45) 80.0% (16/20)

% Live Births/Ongoing Pregnancies 73.3% (33/45) 70.0% (14/20)

% Implantation 63.3% (57/90) 90.0% (18/20)a

% Multiple Pregnancies 58.3% (21/36) 12.5% (2/16)b

All pregnancy rates are expressed/transfer. Results differfrom 2 blastocysts at ap < 0.025 and bp < 0.001 Chi square.

DiscussionIn IVF-ET cases that present 1 high-grade expanded blastocyst( 4AA) on Day 5, reducing the number of blastocysts transferredfrom 2 to 1 had no significant effects on pregnancy or live birthrates. However, reducing the number of embryos transferredfrom 2 to 1 does significantly increase the implantation rate anddramatically reduces the multiple pregnancy rate. These resultsdemonstrate that selective single embryo transfers coupled withblastocyst culture can dramatically reduce the rate of multiplepregnancies without significantly altering pregnancy or live birthrates in IVF-ET cases with 1 high-grade expanded blastocyst( 4AA) on Day 5.

ConclusionsSelective single embryo transfers produce similar pregnancyrates compared to double embryo transfers, while significantlyreducing the multiple pregnancy rate in IVF-ET cases with 1 high-grade expanded blastocyst on Day 5.

References1. Gardner DK, Vella P, Lane M, Wagley L, Schlenker T, Stevens J, Schoolcraft WB.Culture and transfer of human blastocysts increases implantation rates and reducesthe need for multiple embryo transfers. Fertil Steril 1998;69:84-88.2. Gardner DK, Schoolcraft WB, Wagley L, Schlenker T, Stevens J, Hesla J.A prospective randomized trial of blastocyst culture and transfer in in-vitrofertilization. Hum Reprod 1998;13:3434-3440.3. Milki AA, Fisch JD, Behr B. Two-blastocyst transfer has similar pregnancyrates and a decreased multiple gestation rate compared with three-blastocysttransfer. Fertil Steril 1999;72:225-228.

Pregnancy rates are expressed as ongoing pregnancies or livebirths/transfers. Multiple pregnancy rates are expressed as the% of clinical pregnancies with > 1 fetal heartbeat. *** Resultsdiffer from 2 blastocysts at p < 0.001 Chi square.

Graph 1: Selective Single Embryo Transfers Effects on Pregnancy and Multiple

Pregnancy Rates

58.3%

73.3%

12.5%***

70.0%

0.0%

10.0%

20.0%

30.0%

40.0%

50.0%

60.0%

70.0%

80.0%

Ongoing PregnancyRate

Multiple PregnancyRate

2 Blastocysts

1 Blastocyst