Preimplantation genetic screening (PGS) for abnormal number of chromosomes in assisted reproduction.

In IVF and ICSI embryos are selected for transfer on the basis of morphological criteria. Unfortunately, many women fail to become pregnant after an IVF or ICSI treatment. A reason for this could be that the number of chromosomes present in the embryos selected for transfer is abnormal, even though they are 'of good quality'. Preimplantation genetic screening (PGS) is a technique used to identify the number of chromosomes present in embryos created through IVF or ICSI. After PGS, only embryos with a normal number of chromosomes for the chromosomes tested are transferred. PGS has been suggested to improve live birth rates. This review shows that PGS in fact decreases live birth rates in women of advanced maternal age and in women with repeated IVF failure. PGS should not be applied in routine patient care. New forms of PGS that perform the procedure at other stages of development and/or use a different method of analysis should first be evaluated in clinical trials before being introduced into clinical practice.

Authors' conclusions: 

PGS as currently performed significantly decreases live birth rates in women of advanced maternal age and those with repeated IVF failure. Trials in which PGS was offered to women with a good prognosis suggested similar outcomes. PGS technique development is still ongoing in an effort to increase its efficacy. This involves biopsy at other stages of development (polar body or trophectoderm biopsy) and other methods of analysis (comparative genome hybridisation (CGH) or array-based technologies) than used by the trials included in this review. These new developments should be properly evaluated before their routine clinical application. Until such trials have been performed, PGS should not be offered as routine patient care in any form.

Read the full abstract...

In both IVF and ICSI, selection of the most competent embryos for transfer is based on morphological criteria. However, many women fail to achieve a pregnancy even after 'good quality' embryo transfer. One of the presumed causes is that such embryos show an abnormal number of chromosomes (aneuploidies). In preimplantation genetic screening (PGS), only euploid embryos are transferred, with the goal of increasing live birth rates.


To assess the effectiveness of PGS in terms of live birth in women undergoing an IVF or ICSI treatment.

Search strategy: 

In this updated review, the Cochrane Menstrual Disorders and Subfertility Group Trials Register, CENTRAL, MEDLINE and EMBASE were searched to July 2010. This was supported by checking reference lists of included studies and conference abstract books. Authors were contacted for additional data when necessary.

Selection criteria: 

Only randomised controlled trials were selected. They were eligible for inclusion if they compared IVF/ICSI with PGS versus IVF/ICSI without PGS.

Data collection and analysis: 

Relevant data were extracted independently by two reviewers. Trials were screened and analysed according to predetermined quality criteria and disagreements were resolved by a third reviewer. The primary outcome measure was live birth rate per woman. Secondary outcomes were the proportion of women reaching embryo transfer, mean number of embryos transferred, clinical pregnancy rate, multiple pregnancy rate, miscarriage rate, ongoing pregnancy rate, and proportion of women whose child has a congenital malformation.

Main results: 

Nine trials met the inclusion criteria. Live birth rate per woman was significantly lower after IVF/ICSI with PGS compared to IVF/ICSI without PGS in women of advanced maternal age and in women with repeated IVF failure (OR 0.59; 95% CI 0.44 to 0.81 and OR 0.41, 95% CI 0.20 to 0.88 respectively). In good prognosis patients a similar trend was seen, albeit not significant (OR 0.50, 95% CI 0.20 to 1.26, random effects model).