As I was sitting at the annual Pacific Coast Reproductive Society meeting recently, it struck me how fast fertility science’s pace truly is, particularly when it comes to genetic testing of embryos.
The questions that were debated ran the gamut, from practical to ethical: Is it cost effective? Does it improve pregnancy rates or merely pregnancy rates per transfer? Does it come with ethical or emotional costs? Is it the path that will finally lead to more single embryo transfers and thus fewer multiple gestations? Are there embryos that are “over diagnosed,” and if so, do we then discard seemingly abnormal embryos that perhaps would have self-corrected if replaced in vivo?
Statistically speaking, if we just transfer every embryo then, the pregnancy rate per cycle started should theoretically be the same. Eventually we will transfer the desired normal embryo, and the patient will be pregnant.
However, prior to Preimplantation Genetic Screening (PGS), most transfers were done in the fresh cycle. After administering stimulatory drugs, the best embryos were transferred first. And yet, since the early days of egg donation/oocyte recipient cycles, we learned the best implantation rates were in cycles that most closely resembled the natural cycles. So now with PGS and successful vitrification, we delay the transfer to the following cycle. This by itself may improve implantation rates.
Given this insight, the question becomes whether or not we can justify this practice in cycles without PGS? And should we?
When debating such important questions, we must first keep in mind that the woman who is subjected to the transfer of every embryo has her own set of feelings about the situation. For example, let’s say there are twenty embryos and only four are normal. Is it fair or ethical for her to do all twenty single embryo transfers (eSET)? Clearly there is a heavy cost to pay, not just financially, but also physically and emotionally. Somewhere down the line she may demand two or even three embryos be implanted if the transfers keep failing. This then increases the risk of multiples.
As a society, we are imploring doctors and patients to agree to eSET to minimize the risk of multiples, as even twins present much higher risk pregnancies than patients realize. Since the early days of IVF, we placed additional embryos into the womb to maximize chances of success . Today the mindset has shifted: if we can achieve upwards of 70% implantation rates with the transfer of a single normal embryo, then it will be easier for all involved to accept the single transfer. If a patient fails to conceive with a normal embryo, perhaps more work needs to be done to ensure a receptive uterus before she loses another normal embryo.
Continuing on the questions surrounding Assisted Reproductive Technology (ART) and PGS, consider what’s worse than a failed cycle? Is it a negative pregnancy test?
My answer would be no. I believe it’s more upsetting for a woman to go from the thrill of a positive pregnancy test after IVF to a nonviable pregnancy and miscarriage weeks later. Failed pregnancies can leave scars – and I’m not talking about physical ones from, say, a D&C, which is a rarity. My concern is about the emotional impact, which could leave a scar on a patient’s psyche. If it ends up delaying her ability or desire to try again, it may affect her ultimate success rate. Advanced age, and even a fearful, negative mindset that produces high levels of cortisol, may contribute to lower success rates over time.
Critics say the biopsy necessary with PGS may hurt the embryo, and they also like to point out that it can’t diagnose every embryonic abnormality, genetic or otherwise. To note, our age-related “standard” untested pregnancy rates are similar to the age-related percentage of normal embryos, suggesting that many – if not most – failed IVF cycles prior to testing are related to the transfer of abnormal embryos.
In my opinion, utilizing PGS is a kinder and gentler ART. It isn’t perfect, but the couple is given answers. For example, I may tell a couple hoping to conceive, “there were twenty eggs which became fifteen embryos and eight blasts, but only three are normal”. In this case, perhaps there is one abnormal embryo that would have self-corrected, but not using it in my estimation would be a small price to pay to ensure the transfer the first time of a normal embryo with a high chance of success.
PGS is not perfect, nor does it guarantee a pregnancy. But when comparing the pros and cons, particularly in regard to the financial, emotional, and potentially physical costs between doing IVF with and without PGS, I believe the benefits are significant.
To learn more about PGS, please contact the West Coast Women’s Reproductive Center.
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