LIMITING EMBRYO TRANSFERS

Is it time to limit IVF transfers to one embryo?

By Norbert Gleicher, MD

What's the right number of embryos to transfer in each patient? An authority on the subject discusses the newly released ASRM committee guidelines and their practical implications.

Although ovulation-inducing drugs can convert the naturally occurring monofollicular ovarian response into a polyfollicular response, the resulting release of more than one egg significantly increases the risk of multiple conceptions. Widely recognized for decades, it occurs in 5% to 10% of cycles treated with clomiphene citrate and in 15% to 20% of gonadotropin-induced cycles.^1,2

At first, high multiple pregnancy rates were widely accepted and considered a mostly unpreventable complication of successful infertility treatment. But although many patients still welcome multiple births (especially twins and, to a lesser extent, triplets), the medical community's position has evolved.³

That's because the resulting epidemic of multiple births has produced so many premature deliveries over the last few decades; and that in turn has taken a heavy medical, emotional, and economic toll.⁴ Clearly, good infertility care requires doing all we can to reduce the risk of multiples—a consensus that's being echoed by the American Society for Reproductive Medicine's (ASRM) updated committee report guidelines issued this summer. Although the wider use of ovulation-inducing drugs, usually in conjunction with gonadotropins, is more often to blame for this epidemic, much of it has been wrongly attributed to the explosive growth of in vitro fertilization (IVF).^5-7 Such ovulation induction cycles will result in triplets or even higher-order multiples in roughly 9% of all pregnancies.⁸ In contrast, in our experience, if IVF transfer guidelines are followed, the risk of a triplet or higher pregnancy is less than 1%.

Not everyone views twin pregnancies favorably. Most European and Canadian colleagues consider only singleton pregnancies a true IVF treatment success.^9,10 Reproductive endocrinologists in the United States, on the other hand, seem more accepting, perhaps in support of their patients' strong desire for twin pregnancies (more than 60% prefer them over a singleton).^3,11