In more 80 percent of the 41 fertilized ovums tested, the growing and dividing cells failed to form a hollow sphere of about 200 cells, called a blastocyst.
Pioneering British scientists have identified a key gene that may help to explain why so many IVF pregnancies fail.
This study was conducted under a research license with strict regulatory oversight from the Human Fertilisation and Embryology Authority (HFEA) - the UK Government's independent regulator overseeing infertility treatment and research. This gene is also known to help human embryonic stem cells stay flexible enough to become any type of body cell, a property known as pluripotency.
To perform the study, a team led by developmental biologist Kathy Niakan of the Francis Crick Institute in London used a total of 58 embryos that had been generated in fertility clinics as a result of in vitro fertilization (IVF) treatments. What the researchers didn't expect is that OCT4 also affects the development of the placenta precursor cells on the outside of the blastocyst.
"If we are to truly understand human embryonic development and improve human health, we need to work directly on human embryos", he says.
So-called "pluripotent" stem cells whose fate can be manipulated in the laboratory could one day help the tens of thousand of genetic illnesses that have so far been beyond the reach of medical science.
"One way to find out what a gene does in the developing embryo is to see what happens when it isn't working", Dr Kathy Niakan from the Francis Crick Institute said.
The study showed that removing the OCT4-producing gene prevented the embryos form correctly forming the blastocyst, suggesting the gene is key to this process.
Researchers have used genome editing technology to reveal the role of a key gene in human embryos in the first few days of development...
Through this experiment, the team demonstrated the relation between an embryo's development and the OCT4.
"We were surprised to see just how crucial this gene is for human embryo development, but we need to continue our work to confirm its role", said Norah Fogarty of the Francis Crick Institute, first author of the study, which was published Wednesday in the journal Nature. This is basic research which is providing us with a foundation of knowledge about early human development.
"It may take many years to achieve such an understanding", Niakan said. However, it is the first time the technique is used to study the process of early human development to understand better why some women miscarry after going through IVF.
They discovered important differences at the molecular level between developing embryos from the two species.
Before beginning experiments on human embryos, the scientists spent a year optimizing their work on mice embryos and human embryonic stem cells.
In August, scientists in the United States said they had repaired a disease-causing mutation in the DNA of early-stage human embryos using CRISPR-Cas9 - although other teams have expressed doubts about their conclusions.