New study finds ways to improve IVF success rates

By Stephen Beech via SWNS

The chances of IVF treatment being a success have been improved following a major new study.

Researchers studied thousands of fertility attempts - and their findings have discovered new ways to sustain embryos as development begins.

Scientists at London Women’s Clinic and Johns Hopkins University compared hundreds of IVF embryos that failed to develop within a few days of fertilization with embryos that survived, looking for genetic differences.

Their findings, published in the journal Genome Medicine, have provided the most detailed analysis of embryo fate following human IVF, or in vitro fertilization.

Almost half the embryos studied underwent developmental arrest because of genetic mishaps in early development, according to the research team.

They described it as a revealing insight that suggests more IVF babies could come to term with changes in the fertility treatment process.

The unique combination of data from arrested embryos also sheds new light on the still largely mysterious earliest stages of pregnancy through natural means.

Study author Dr. Rajiv McCoy said: "We think this also happens in natural conception, and it’s why it takes on average several or more months to get pregnant.

“It is very surprising that most of these embryo arrests are coming not from errors in egg formation, but from errors happening in cell divisions after fertilization.

"The fact that these errors don’t come from the egg suggests that maybe they could be mitigated by changing the way IVF is done.”

Dr. McCoy, an Assistant Professor of biology at Johns Hopkins, added: “Genetic testing is typically only done on IVF embryos that survive in order to decide which embryo to transfer to the uterus.

“But from a biology standpoint, if we want to understand what's allowing these embryos to survive, then we have to test all other embryos too.”

The findings reveal how some embryos start growing properly while the maternal genetic material pre-loaded into the egg control cell division, only to falter and stall when the embryo’s genes take over.

Human cells typically receive 46 chromosomes, 23 from each parent.

The team discovered nonviable embryos started with the 46-chromosome set, but then passed down incorrect numbers of chromosomes as cells divided.

Dr. McCoy said: “It doesn’t really matter if you have extra missing chromosomes in the very beginning because the maternal machinery is controlling things.

“When the embryo’s genome turns on, that’s when things go wrong.”

He explained that human embryos experience unusually high rates of chromosome gain and loss, known as aneuploidy, in early development.

Scientists have studied aneuploidy for decades by screening IVF embryos, and the mishaps are well understood to be the cause of pregnancy loss in humans.

Dr. McCoy said that because aneuploidy is rare in many other species, the findings could help explain why pregnancy loss and miscarriage are so common in humans.

He added: “Aneuploidy is an example of an extremely strong type of natural selection that’s going on every generation in humans.

“It might just be a feature of human reproduction and development, but it has implications for IVF.

"So in the long term, we hope that we can improve genetic testing and improve IVF outcomes.”

The researchers plan to run further tests on specific cells from arrested embryos to trace the chromosomes’ origins and see whether abnormal cell divisions are linked to maternal or paternal genetics.

They also want to better understand if factors such as the chemical composition in the dish where the embryos are grown could improve chances for survival.

Co-author Michael Summers, Senior Consultant in Reproductive Medicine at London Women’s Clinic, said: “We could potentially correct a lot of these things by understanding more about the machinery that causes embryo arrest."

He added: “The problem could be that the chemical composition of the culture medium that are commonly used will not allow all embryos to grow, that the abnormal cell divisions are due to stresses on the egg and early embryo that causes the abnormal divisions associated with chromosome abnormalities.”