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Preimplantation Genetic Screening and Pregnancy Outcome

In two European IVF centers, preimplantation genetic screening was associated with lower pregnancy rates among older women.

Pregnancy rates generally decrease as women age, a likely reflection of the increasing numbers of chromosomally abnormal embryos. In women of advanced maternal age who are undergoing in vitro fertilization, pregnancy rates theoretically should increase if embryos are prescreened and only chromosomally normal embryos are transferred. In this study, 408 women (age range, 35–41) scheduled to undergo IVF in one of two Dutch centers were randomly assigned to standard IVF with or without (control) preimplantation genetic screening (PGS) and were followed for three cycles. No more than two embryos were transferred during any one cycle.

In both the PGS group and the control group, approximately one third of the participants discontinued treatment (77 of 206 vs. 71 of 202). Of 434 follicular aspirations with PGS, 48 resulted in ongoing pregnancies (11%). Of 402 aspirations with standard IVF, 66 resulted in ongoing pregnancies (16.4%). Results of an intent-to-treat analysis showed that significantly fewer patients in the PGS group, compared with the control group, had ongoing pregnancies: 25% (52 of 206) versus 37% (74 of 202).

Comment: The results of this well-performed controlled trial suggest that PGS should not be used in older women undergoing IVF. One third of the women dropped out before completing three IVF cycles, yet the authors still include these women in their intent-to-treat analysis of outcome. Based on the actual follicular aspiration rates rather than the intent-to-treat numbers, the ongoing pregnancy rate is still lower for the PGS group. The most important information imparted by this study, which reflects experience in two relatively small centers rather than worldwide experience, is that PGS outcome is likely to be highly center- and operator-specific.

— Sandra Ann Carson, MD

Published in Journal Watch Women's Health July 12, 2007

Citation(s):

Mastenbroek S et al. In vitro fertilization with preimplantation genetic screening. N Engl J Med 2007 Jul 5; 357:9-17.

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