11 June 2009

Calculating Fertility

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Embryo selection techniques are now being taken one step forward with the introduction of new criteria

We don’t really seem to know all that much about the organ we all come from. Professor Robert Winston, a leading light in fertility treatment from Hammersmith Hospital in London, has defined the uterus as “highly dynamic and complex”, but uterine receptivity has been poorly understood so far despite its being so crucial to the survival of the species. One thing is sure, conventional IVF looks increasingly unsatisfactory to both women and doctors, although demand for it seems to have never been higher. The safety and efficacy of certain processes, such as heavy ovarian stimulation, are already in the line of fire. On the other hand, some scientists have been trying to improve women’s odds by focusing on the quest for the “best embryo”, or the “best egg” to implant.

Pre-implantation screening diagnosis for certain conditions is already a given, such as the recent success of a medical team in selecting the embryo of a British baby girl who will grow up to be free of the BRCA-1 breast cancer gene that has stricken the paternal side of her family again and again. Only one other mother, an Israeli woman, is thought to have become pregnant after undergoing this screening.

However, embryo genetic screening, while not looking for specific diseases, is just meant to identify an embryo at risk. These selection techniques are now being taken one step forward with the introduction of new criteria. Again, Professor Winston has said that the good quality of an embryo depends on the good quality of the egg. But endometrial receptivity, and perhaps even egg quality itself, may be impaired by the oestrogen bomb released by the ovary-stimulating drug cocktails, as some studies have indicated, not to mention the risk of ovarian hyperstimulation which may, in rare cases, be fatal. Professor Winston said at least half , “if not 70%” of all eggs harvested from women undergoing IVF contain damage to their DNA. “New studies are needed to prove the drugs are causing the damage, but it is my strong suspicion that this is the case”.

Indeed, this hormonal upheaval may not even turn out to be indispensable to all women. Those with polycystic ovary syndrome may benefit just as well from the so-called “soft IVF” or IVM (in vitro maturation) involving a much milder hormonal hit. This method has the advantage of being cheaper and not producing risky multiple pregnancies, not to mention the fact that it can be repeated more often.

Some people have come to think standard IVF may be caught in a partially self-defeating loop. Others, like Professor Geeta Nargund, head of Reproductive Medicine at St. George’s Hospital in London, are alarmed at the overuse of drugs in fertility treatment. Back in 2006 Dr Nargund criticized those fertility clinics that don’t stick to recommended dose levels.

Even the technique of embryo freezing is being openly questioned again by some, with the allegation that it might cause chromosomal abnormalities in the pre-implantation phase. If this were true, some researchers say, it could conceivably be the case that many IVF recurrent miscarriages occur because the uterus is just rejecting a defective embryo.
But the problem cannot be liquidated so easily, and lots of other research has gone into probing the immunological response that can often put an IVF pregnancy at risk, including the role of the usual suspects, including maternal Natural Killer Cells going into overdrive.

The quest for an IVF technique that does not impair itself, and which does not put women’s health at risk, continues. In their drive to improve on admittedly modest success rates, some scientists have chosen to focus on the “molecular conversation” between uterus and embryo. The underlying secrets of womb receptivity and its possible predictors, such as a uterus artery ultrasound, are being pushed to the fore again.

 

 

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