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.
Preimplantation genetic screening does not improve delivery rate in women under the age of 36 following single-embryo transfer.
Single-embryo transfer is a well-accepted strategy to avoid multiple pregnancies in an assisted reproductive technology (ART) programme. Besides the morphological quality and embryo kinetics up to the blastocyst stage, preimplantation genetic screening (PGS) of aneuploidy has been advocated as an adjuvant approach to select the embryo.
                Couples with a female partner younger than 36 were randomly assigned to undergo transfer of a single blastocyst in a cycle with or without PGS using FISH for the chromosomes X, Y, 13, 16, 18, 21, 22.
                After the enrolment of 120 of the projected 447 patients in each group, study recruitment was terminated prematurely on the basis of futility. The observed live birth delivery rates after ART were 30.8 versus 30.8% per randomized patient, 34.6 versus 34.6% per cycle initiated, 37.8 versus 37.0% per aspirated cycle and 41.6 versus 43.5% per embryo transfer for the control versus the PGS group, respectively, with absolute between-group differences (95% CI; P value) of 0% (-11.7 to 11.7; P = 1.00), 0% (-12.7 to 12.7; P = 1.00), -0.8% (-14.2 to 12.7; P = 0.91) and 2.1% (-12.7 to 16.7; P = 0.79), respectively. Even in this younger age group, only 61% of the embryos had a normal diploid status.
                The absence of a beneficial treatment effect in this randomized clinical trial provides no arguments in favour of PGS to improve live birth delivery rate following single-embryo transfer in women under the age 36. Clinical Trials.gov: NCT00670059.