PGT-A

Should I do PGT-A?  I get asked this every day.

 

About 1 in 4 of the patients I see need to do IVF to conceive.  IVF involves stimulating the ovaries with injections of FSH to grow multiple eggs.  We then take out the eggs that were stimulated through the vagina and fertilize them with sperm to make embryos.  These embryos are grown in our lab for 5-7 days - until they either become blastocyst stage embyos or stop growing (because they aren’t healthy enough to become blastocysts).

 

When we have blastocysts, patients can do one of three things with them:

 

  1. put them into their uterus right away - a fresh embryo transfer
  2. freeze them for a later frozen embryo transfer 
  3. biopsy them to see if they are chromosomally normal - called PGT-A

 

I review these options with patients and give them my best advice for their particular situation.  

 

Who should do PGT-A?

 

Well at the American Fertility Society meeting currently underway in Denver there are numerous studies being published on PGT-A, indeed it is a real focus of this meeting.  Several research and clinical groups, like ours, are trying to answer this question.

 

A key study, called the STAR study, has released its data, a large PGT-A centre in Spain has reported their data on PGT-A  and several other smaller groups have studies they have reported today. My job is to sort through all this new and exciting information and then personalize it to my patients.  What is my distillation of who should do PGT-A?

 

You should do PGT-A if you have:

 

  • previous child with a chromosome abnormality
  • repeated miscarriages
  • previous failed IVF cycle(s)
  • medical or uterine reason to avoid a miscarriage or D&C

 

If you have one or more of these issues, you should probably do PGT-A.  If you are 38 years or older, you should probably do PGT-A too (whether you have any of these issues) as you are less likely to miscarry with PGT-A and will get pregnant faster then if you do not do PGT-A on your embryos. This is because you are more likely to have a baby if you know you are putting in a chromosomally normal embryo.  If you don’t do PGT-A, and you are 38 or older, you are quite likely putting in a chromosomally abnormal embryo which can cause miscarriage or a negative pregnancy test.

 

If you are under age 35 you should probably not do PGT-A (STAR study). If you are between 35-38 it depends on the situation - that requires more consideration.

 

Not everyone agrees with me on these reasons.  A program similar in size to us in Oregon has 90% of patients doing PGT-A (we are about 50%).  I can back up my advice with research though.  I will admit that I have not factored in the financial part of decision-making.  PGT-A costs an additional $4000-5000 on top of the IVF cycle, so the cost matters for most people.  I have also not factored in number of embryos obtained from IVF, either.  If you get a LOT of embryos from an IVF cycle, PGT-A almost always makes sense if you are over 35.  If you only get 1 embryo it might not make sense to do PGT-A, depending on the situation.

 

What the studies reported to date support is that if you do not factor in the cost, PGT-A makes sense for women >= 38 years old and makes less sense if you are < 35 years old.

 

 

Currently to do PGT-A you need a sample of cells from the embryo to test.  The process of removing the cells from the embryo (the biopsy) can potentially harm an embryo which is possibly why PGT-A doesn’t help women under 35 as you are likely biopsying normal embryos and potentially causing harm.  So, the next step is to get chromosome information from embryos without doing a biopsy. This is called non-invasive PGT-A (niPGT-A).  It’s done by collecting the fluid around the embryo as it grows in the lab. We know the embryos will shed some genetic material as they grow.  This genetic material can be extracted from the fluid and tested.  So far groups have shown a decent (70-85%) agreement between biopsy samples and the fluid samples so we are getting close. Once the science advances so that the fluid testing is as accurate as biopsy testing (95%+ agreement) we will stop biopsying embryos.  I think we are about 1-2 years away from this.

 

It’s all very exciting stuff.  I am proud that we are at the forefront of these exciting advances in IVF.  Meetings like today get us charged up to keep learning and reseaching and finding new ways to improve outcomes for our patients.

Dr. Beth Taylor MD, FRCSC
Reproductive Endocrinology & Infertility