Comprehensive Chromosome Screening and IVF Success Rates

Blastocyst Biopsy With Comprehensive Chromosome Screening and Fresh Embryo Transfer Significantly Increases In Vitro Fertilization Implantation and Delivery Rates: a Randomized Controlled Trial

Scott RT Jr, Upham KM, Forman EJ, et al
Fertil Steril. 2013;100:697-703

The Study

Most experts agree that assisted reproductive technology (ART) outcome is ideal when a healthy, full-term singleton is born. The past few decades have seen an epidemic of multiple pregnancies, including high-order multiple pregnancies.

There are various factors responsible for this trend. Multiple pregnancies are more common during the later reproductive years, and the recent trend of delaying childbearing has resulted in more spontaneous multiple pregnancies. In vitro fertilization (IVF) is also responsible for some of the additional multiple pregnancies, and other forms of ART contribute their share.^[1]

During IVF, it would be easy to avoid multiple gestations by the transfer of a single embryo only. The number of embryos transferred has continuously declined over the years -- but still, in the majority of the cycles, more than 1 embryo is replaced to maintain high success rates. The number of high-order multiple pregnancies has decreased significantly, but the rate of twin pregnancies has not changed.^[2] Even a singleton pregnancy conceived through ART is associated with higher risks compared with spontaneously conceived singletons, and twins carry additional risks.^[3,4]

Unless a policy is made to transfer only a single embryo, it will not become routine practice for all patients, because unfortunately, the majority of embryos created in vitro and selected on the basis of their morphology will not implant. The past few years have seen significant improvements in technologies aiding embryo selection, and they could provide us with effective tools to identify the single best embryo to transfer.

Genetic screening of embryos is an area that has undergone tremendous improvements. So far, however, relatively few and small randomized studies have shown its clinical efficacy in highly selected groups of patients. This study is an adequately powered randomized trial studying the benefits of preimplantation genetic screening of embryos.

This randomized, controlled trial assessed the benefits of quantitative real-time polymerase chain reaction comprehensive chromosome screening (CCS) on implantation and pregnancy rates during IVF. Women younger than 42 years who had normal ovarian function and no more than 1 previous IVF failure were eligible. In addition, the patients had to have at least 2 good-morphology blastocysts to be randomly assigned to CCS or standard care (morphologic selection).

In the CCS group, biopsy of the blastocyst was done on day 5, and the transfer was performed the next day. In the standard care group, transfer was done on day 5. A maximum of 2 embryos were replaced.

After initial recruitment of 288 patients, 155 (72 in the CCS group and 83 in the control group) were randomly assigned. The mean age of the patients was 32 years, and they produced on average 17 eggs. The mean number of blastocysts on day 5 was 8 in the CCS group and 7.9 in the control group. The mean number of transferred embryos was 1.8 in the study and 2 in the control group.

The implantation rate was higher in the CCS group (79.8% vs 63.2%; RR: 1.26; 95% CI, 1.04-1.39). Clinical pregnancy rates were also higher in the CCS group (93.1% vs 80.7% of the cycles; RR, 1.15; 95% CI, 1.03-1.43). Delivery rates were also superior in the CCS group.

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