Definition - What does Embryo Arrest mean?
Embryo arrest is when an embryo stops growing before becoming a blastocyst in the laboratory during an in vitro fertilization (IVF) procedure. A lack of growth means that the cells stop dividing during the cleavage or morula stage of development (before Day 5.)
The arrest of one or even a few embryos is normal during a procedure, but having a high rate of embryo arrest can even predict IVF failure, requiring further cycles.
FertilitySmarts explains Embryo Arrest
During IVF, eggs are extracted and fertilized with sperm in a laboratory setting, and the most promising embryo/s are transferred to the uterus for further development. If a significant number of embryos stop growing in the laboratory setting, there could be few or even no embryos to transfer to a uterus.
What causes embryo arrest?
Embryo arrest can be due to factors related to the embryo as well as factors in the environment that the embryo develops in.
For an embryo to undergo normal development, the sperm and the egg that created the embryo need to be healthy and the environment that the embryo grows in, typically a culture medium in a laboratory dish, has to be optimum. A change in any one of these factors can impact cell division and maturation can be slowed down or completely halted leading to embryo arrest.
The composition of the culture media plays an important role in the development of embryos. Any fluctuation of the temperature, pH, humidity, and entry of bacteria to the culture medium can result in embryo arrest. The IVF laboratory usually monitors the environmental conditions and the growing embryos are regularly observed for any abnormalities, but lab errors causing embryo arrest remains a possibility.
Nearly 50% of embryos that arrest do so because of chromosomal abnormalities. When the sperm fertilizes an egg, the two sets of chromosomes that each cell possesses a pair together and are shared in equal numbers as the embryo further divides.
Any abnormality either in the structure or number of these chromosomes can interfere with the normal development of the embryo. Failure to activate genes that are needed for cell division is another embryo-related cause of embryo arrest.
If embryos completely arrest, they are discarded as they can interfere with the development of other embryos.
- Permanent embryo arrest: molecular and cellular concepts. (2008).
- Chromosomal Aneuploidies and Early Embryonic Developmental Arrest. (2015).