Majority of Blastocyst-Stage Embryo Transfers in Young Women Are Noncompliant With Recommended Transfer Limits

More than 60% of blastocyst-stage embryo transfer cycles performed in 2013 involved the transfer of at least 2 embryos in women younger than 35 years of age with a favorable prognosis, despite recommendations for single-embryo transfer in this patient subgroup. These findings, which represent the most recent data available from the national registry of the Society for Assisted Reproductive Technology (SART), highlight the ongoing challenge of minimizing multiple birth rates among women undergoing in vitro fertilization (IVF).

Sanaz Keyhan, MD, a fellow of the Division of Reproductive Endocrinology and Infertility at Duke University Medical Center, presented results from the study at the Scientific Congress & Expo of the American Society for Reproductive Medicine (ASRM), held October 15 to 19, 2016, in Salt Lake City, UT.

Multiple births from assisted reproductive technology increase the risks of perinatal and maternal morbidity and mortality compared with singleton births. To minimize the number of multiple pregnancies, the ASRM and SART developed recommendations in 2013 for embryo transfer based on patient age and prognostic features.

Favorable prognosis is defined as any of the following: first cycle of IVF, good embryo quality, excess embryos available for cryopreservation, or previous successful IVF. The recommended limits on the number of embryos to transfer in women aged younger than 35 years with a favorable prognosis are 1 to 2 for cleavage-stage embryos and 1 for blastocyst-stage embryos.

In the present retrospective cohort study, researchers analyzed first fresh autologous IVF cycles in women aged younger than 35 years with excess cryopreserved embryos undergoing embryo transfer. IVF results were stratified by embryo stage at the time of transfer: cleavage stage (day 2/3) or blastocyst stage (day 5/6). The primary end points were rate of noncompliance with the 2013 guidelines from ASRM and SART for embryo transfer and the multiple pregnancy rate.

A total of 2,249 IVF cycles were included in the study. Of these, 1,768 (79%) involved blastocyst-stage embryo transfers and 481 (21%) involved cleavage-stage embryos.

Among blastocyst-stage embryo transfer cycles, 1,079 (61%) were noncompliant with recommended transfer limits (Table 1). A similar number of oocytes were retrieved from patients in both groups. However, compared with patients in the compliant group, patients in the noncompliant group had a significantly higher clinical pregnancy rate, live birth rate, multiple live birth rate, and multiple pregnancy rate (see Table 1).

Table 1. Blastocyst-Stage Embryo Transfer Cycles in Women Aged < 35 y 

Variable Compliant (n = 689) Noncompliant (n = 1,079) P Value
Oocytes retrieved, mean 18.6 18.0 .15
Embryo transfers, mean (range) 1.0 (1) 2.0 (2-3) < .001
Embryos cryopreserved, mean 5.2 4.2 < .001
Clinical pregnancy rate, % 60.7 68.5 < .01
Live birth rate, % 53.7 60.0 < .05
Multiple live birth rate, % 2.4 42.6 < .01
Singleton live birth rate, % 97.0 49.8 < .001
Multiple pregnancy rate, % 3.0 50.2 < .001


“If the optimal measure of success in IVF is a healthy singleton baby, clinics need to be compliant with the ASRM and SART guidelines by transferring a single blastocyst in women who are younger than 35 years old with a favorable prognosis,” Keyhan said.

The vast majority (97.1%) of cleavage-stage embryo transfers were compliant in transferring 1 to 2 embryos (Table 2). Even among compliant transfers, however, the multiple live birth rate was 34.3%. All pregnancy outcomes were similar in both groups.

Table 2. Cleavage-Stage Embryo Transfer Cycles in Women Aged < 35 y

Variable Compliant (n = 467) Noncompliant (n = 14) P Value
Oocytes retrieved, mean 13.8 14.1 .84
Embryo transfers, mean (range) 1.9 (1-2) 3.0 (3) < .001
Embryos cryopreserved, mean 3.5 3.1 .69
Clinical pregnancy rate, % 56.6 71.4 .30
Live birth rate, % 52.7 50.0 1.0
Multiple live birth rate, % 34.3 14.3 .44
Singleton live birth rate, % 64.7 70.0 1.0
Multiple pregnancy rate, % 35.3 30.0 1.0


In 2016, ASRM and SART proposed updated recommendations for embryo transfer that are more conservative than the 2013 criteria. The 2016 guidelines recommend transferring 1 embryo for cleavage-stage embryos and blastocysts for women up to the age of 37 years who have favorable prognoses.

The definition of favorable prognosis for fresh IVF cycles has also been revised to include any 1 of the following: the transfer of euploid embryos, the expectation of 1 or more high-quality embryos available for cryopreservation, or a previous live birth after an IVF cycle. First cycle of IVF is no longer a favorable prognostic factor.

“These most recent criteria are definitely a move in the right direction by reducing the number of embryos that are recommended for transfer,” Keyhan said.

Source: Keyhan S, Acharya KS, Acharya RC, Li SJ, Muasher SJ. Are we transferring too many embryos in the most favorable group of fresh autologous IVF cycles: a 2013 update. Presented at: American Society for Reproductive Medicine 2016 Scientific Congress & Expo; October 15-19, 2016; Salt Lake City, UT. Abstract O-131.