When It Doesn't Work
IVF works most of the time in couples where the female age is under 40. When it doesn't work, we ask: is it the embryo or is it the woman? With more widespread use of chromosome screening of embryos -- called Comprehensive Chromosomal Screening (CCS) or Preimplantation Genetic Screening (PGS) -- the embryo is less likely to be the culprit.
In other words, since we can now select chromosomally-normal embryos before we put them into a woman's uterus during IVF, it is now more likely the woman will get pregnant. If she doesn't, it is more likely due to the woman, not the embryo.
Personally, I am surprised as how often a chromosomally-normal embryo does not implant (about 25% of the time) and how often it miscarries (15%). Why does a woman not get pregnant after putting a chromosomally-normal embryo into her uterus?
There are plenty of reasons that we can test for:
- uterine polyps
- uterine fibroids inside the cavity (called submucous fibroids)
- untreated hydrosalpinx
- uterine infection
- thyroid disease
These are all manageable, but there are cases we cannot explain. All the testing is normal in the woman, yet a chromosomally normal embryo does not implant. This is incrediably upsetting and frustrating. The focus of much of IVF research is now on these implantation failures of normal embryos. We are looking at progesterone status, immune factors, cell adhesions molecules, etc. This research cannot happen fast enough for our couples with this problem.
What do we do for couples when chromosomally-normal embryos do not implant? We go back to the drawing board and make sure every fixable factor has been fixed. Sometimes, we tweak the drug protocol. Sometimes we suggest they use a surrogate.
I think the future is endometrial testing prior to any embryo transfer to make sure all the cytokines, adhesion molecules, growth factors, lipids, etc. are in "receptive" concentrations in the uterus. We'll then treat any deficiencies prior to transfer. We are likely years away from such therapies, unfortunate for those (few) women who do not implant chromosomally normal embryos.