The embryo won't survive if the egg is fertilized. There are a lot of things that can go wrong in the first few weeks.
Each of the two resulting cells can receive an exact copy of the fertilized egg's entire genome. Each time a cell splits, this process must be repeated.
Sometimes, it can miss a chromosomes.
Scientists don't know why this happens so frequently in early embryos, but they are close to figuring it out.
It is difficult to decipher the genome of the early embryo.
Human reproduction isn't flawless. Some embryos fail to implant into the uterus lining in the first few weeks of fertilization.
The egg is fertilized in the lab which is inefficient. Between 4 and 50 percent of artificially fertilized eggs actually implant and make it to birth, depending on the age of the person.
Sixty percent of fertilized eggs in the lab have an abnormal number of chromosomes.
The origins of these early genetic errors are not well understood.
When a cell is pulled apart into two identical daughter cells, one of the chromosomes may end up in the wrong cell, leaving two copies in the other cell.
A new study shows that the problem can start early.
Some chromosomal abnormality may arise from the very first stages of cell division, according to researchers.
A broken or fragmented chromosomes can be caused by genetic sites that don't get replicated correctly. The wrong number of chromosomes is caused by the mechanism that pull the chromosomes apart.
These errors could be carried on by subsequent cell divisions. The embryo's demise can be caused by the mistakes ending up in enough cells.
The researchers don't know what causes the initial damage, but they think it has something to do with the interference of molecules that turn genes on and off
A break in the double strand could result in chromosomal abnormality. The authors don't know if the changes were present in the egg or sperm before or after fertilization.
The integrity of the genome is a critical requirement for normal development and this has largely been overlooked in previous studies.
One day, if researchers can figure out which signs of DNA damage to look out for in an early embryo, then IVF could become more efficient. It's probably not worth implanting if the cell doesn't duplicate its genes in the first stage of cell division.
Many women undergoing fertility treatment need multiple IVF cycles in order to get pregnant and some never get pregnant at all.
This is emotionally taxing.
The authors want to make assisted reproduction less heartbreaking for prospective parents.
The study was published in a scientific journal.
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