Embryo Selection

A Toss-up

The process of generating embryos for in vitro fertilization (IVF) is still undergoing a process of refinement. It's been somewhat of a toss-up to decide which embryos might yield the most successful, healthy results. Now Australian researchers have developed a new screening method that appears to select those embryos for IVF that have the greatest chance of becoming healthy babies.

The Aussie researchers, according to a report in Human Reproduction, employ DNA fingerprinting, or an evaluation of the active genes in a cell, to improve IVF success rates, raising the number of pregnancies brought to term, and lowering the chance of birth defects. Until now, choosing which 5 day old embryos would be transferred in the IVF process was based on the shape of the embryos and other such unproven techniques. The researchers believe that this new method of selection will also cut the number of multiple births resulting from the IVF process, since up to now, in the absence of precise methodologies for embryo selection, doctors have chosen to implant multiple blastocysts in their efforts to increase the rate of conception.

The Australian study reports that IVF has a conception rate of 42%, with 32% going on to give birth to twins or multiples. The risk of complications during pregnancy and delivery rises with each embryo carried. A multiple pregnancy often necessitates a C-section, and can result as well in low birth weights or birth defects.

Co-authors of this study, Gayle Jones and David Cram, both senior research scientists in immunology and stem cells at Australia's Monash University wrote,  "What we want this technology to achieve is confidence to switch to single embryo transfers instead of the practice of transferring multiple embryos without [a  coexistent] reduction in pregnancy rate."

Major Glitch

This is a lofty goal since the major glitch in IVF is finding a way to increase the rate of success while reducing the number of multiple births.

The researchers took between 8 and 20 cells from the outer layer of the blastocysts of 48 women undergoing the IVF procedure. This outer layer is called the trophectoderm and consists of a group of cells that when mature, becomes a placenta. The placenta is the sack that holds and protects the embryo while it inside the mother's uterus, providing it with nutrients culled from the mother's body and removing the fetus' waste products. These cell samples were then scanned with microarray technology. This process divides genetic material into sections. This enables the researchers to determine which cell-contained genes are active and which are at rest.

Conception success rates were very good with 25 of the participants becoming pregnant after implantation. These pregnancies resulted in 37 babies, with half of the pregnancies consisting of more than one child.

Researchers believe the process can be refined giving even better results in the future as they narrow down the list of which genes are most likely to succeed. Other scientists comment that this is the science of the future with a great deal left to learn before the process of embryo selection can become a scientific formula.

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