Two women taking part in the world's first controlled study of a comprehensive genetic screening test before IVF have given birth to healthy babies. The babies, twin girls born in Germany in June and a singleton boy born in Italy in September, are the first deliveries in a pilot study of comparative genomic hybridisation (CGH) by microarray, a new method of screening oocytes for IVF for a full range of chromosomal disorders.
Dr Cristina Magli, embryologist at the SISMER Centre in Bologna, one of the two centres taking part in the trial, said: " All the babies and their mothers are doing very well in terms of weight and overall developmental performance."
One goal here is to increase the rate of successful pregnancies when doing in vitro fertilization (IVF). But continued improvement in embryo selection techniques inevitably will lead to healthier babies since some flaws that aren't bad enough to cause miscarriage will also be avoided. Big strides in embryo selection will very likely eventually lead to healthier babies via IVF than via natural sexual reproduction.
Once the stage is reached where IVF is safer then starting a pregnancy in the lab will become preferred by a substantial percentage of the population. What comes next? Selection of embryos for a larger list of reasons having to do with physical appearances, athletic ability, intelligence, personality, and other attributes.
The births, as well as several ongoing pregnancies in the study group, are the final stage in the "proof of principle" that the screening of oocytes and embryos before transfer in IVF can increase birth rates; both these pregnancies were derived from oocytes whose complete chromosomal status had been assessed by microarray CGH.
The study, which was conducted in Bologna, Italy, and Bonn, Germany, was designed and organised by a task force of ESHRE to determine the clinical value of CGH as a non-subjective means of genetic screening before embryo transfer.
A substantial fraction of all embryos miscarry in humans.
Another recent report on techniques for identifying healthy embryos shows that while most human embryos fail to reach the blastocyst stage it is possible to predict which ones will succeed.
STANFORD, Calif. — Two-thirds of all human embryos fail to develop successfully. Now, in a new study, researchers at the Stanford University School of Medicine have shown that they can predict with 93 percent certainty which fertilized eggs will make it to a critical developmental milestone and which will stall and die. The findings are important to the understanding of the fundamentals of human development at the earliest stages, which have largely remained a mystery despite the attention given to human embryonic stem cell research.
A much higher percentage of human embryos fail to reach blastocyst stage. Lots of silent failures of conceptions to fail to turn into detectable pregnancies. If life begins at conception then most humans die undetected.
"In mice, about 80 to 90 percent of embryos develop to the blastocyst stage. In humans, it's about 30 percent," said Reijo Pera. "In addition, about one in 100 mouse embryos are chromosomally abnormal, versus about seven out of 10 human embryos. That's why human studies like these are so important. Women, their families and their physicians want to increase the chances of having one healthy baby and avoid high-risk pregnancies, miscarriages or other adverse maternal and fetal outcomes. It's truly a women's health issue that affects the broader family."
Why the higher rate of chromosome abnormality in human embryos? Does this happen as a result of some complex method of checking by the cells about whether they have good genetic integrity? There's a much bigger investment by parents in a human's development than is the case with mice. So tossing out questionable embryos at a very early stage of development reduces the costs of poor investments.
I see two parallel threads of biotechnological advance that will spur a shift toward IVF as the preferred method for starting human pregnancies: A) Better ways to detect defects in IVF embryos to the point where IVF becomes the safer choice; and B) knowledge derived from cheap genetic sequencing that will identify the significance of most genetic variants. Once IVF becomes safer and it becomes a way to select for desired genetic traits IVF will become the preferred way to start pregnancies, especially for the most ambitious parents.
|Share |||Randall Parker, 2010 October 17 10:42 PM Biotech Reproduction|