PGT is just one more tool to narrow down the choice of embryos for transfer into the uterus. This is why PGT improvement in pregnancy is only “pre-transfer”, not “per-patient”. This distinction has very high practical importance. For example, if a patient starts an IVF treatment cycle, but has no chromosomally normal embryos by PGT to transfer, the cycle is excluded from calculating the “pre-transfer” pregnancy rate. Consequently, the pregnancy rate per transfer with (or without) PGT is always higher and may mislead some patients into believing that everyone benefits from PGT.

In reality, PGT has never been convincingly shown to improve the chance of pregnancy or reduce the probability of miscarriages. This goes against rational expectations. The most likely reasons why PGT has not fully met its expectations are probably two:  

1. Embryo biopsy itself can be damaging to the embryo
2. The risk of false positives and mosaicism 

A careful assessment of the embryos is the first step in making a decision, where an embryologist’s experience plays a crucial role. She is the only one who is qualified to answer the following question about each embryo: can I safely remove the number of cells necessary to perform the testing without reducing embryo viability? Based on her answer, she can make a recommendation to a physician or a patient.

To this end, it may be useful to keep in mind that some embryologists believe that biopsy is never safe for an embryo, while others that it is never detrimental. Therefore, if you are a concern (and you must be), make a point to ask a physician and embryologist position on the issue before you start an IVF cycle.    

When PGT is a must

There are cases when PGT is a must regardless of any other circumstances:

1. The patient will not terminate a pregnancy with a fetus affected by Down syndrome or by another genetic defect compatible with life and tries to avoid any chance of such pregnancy.
2. The patient’s sole reason for seeking IVF is gender selection.

PGT to avoid miscarriage

Miscarriage can be very traumatic. Yet, it is estimated that at least 50% of natural conceptions end up with miscarriage and it has a positive prognostic value for subsequent childbirth. It is very important to balance the risk of another miscarriage against losing an otherwise viable embryo to an extended culture, embryo biopsy, and false-positive PGT testing results. Another point to keep in mind is that in younger patients only about half of the miscarriages are due to chromosomal errors in embryos. On the other hand, patients of advanced reproductive age often may simply not have enough embryos to justify an extended culture and embryo biopsy. 

How to think about making decision considering PGT

Ask yourself the following question.

Suppose I do not have fertility problems and can conceive naturally, would I instead choose IVF in order to be able test my embryos for chromosomal errors?