The only way to be sure is to use ultrasound to see whether there are one or more gestational sacs and to detect the fetus or fetuses via their heartbeats. It can be difficult to identify whether a multiple pregnancy has occurred after true zygotic splitting or as a result of SET combined with sexual intercourse that results in another egg being fertilised at the same time. These are known as "monozygotic" twins (or triplets). Zygotic splitting occurs between days two and six when the zygote divides, usually into two, and each zygote then goes on to develop into an embryo, leading to identical twins (or triplets if it divides into three).
It soon starts to divide and subdivide into many more cells called blastomeres, which eventually form the embryo. One of the authors of the study, Dr Keiji Kuroda, of the Sugiyama Clinic Shinjuku and Juntendo University Faculty of Medicine in Japan, said: "As a result of our findings, clinicians may want to consider whether they should counsel couples about the small increase in the risk of multiple pregnancies as a result of zygotic splitting associated with some embryo manipulations."Ī zygote is the fertilised egg cell that results from a man's sperm fertilising a woman's egg, and it contains all the genetic information from both parents to form a new individual. These include using frozen thawed embryos for SET, maturing the fertilised egg (blastocyst) in the laboratory for five or six days before SET, and assisted hatching, in which a small hole is created in the layer of proteins surrounding the embryo (the zona pellucida) to help the embryo hatch out and attach itself to the wall of the woman's womb. These results come from the largest study to investigate zygotic splitting after SET - it analysed 937,848 SET cycles - and it highlights factors that could increase the risk.
In a study published today (Tuesday) in Human Reproduction, one of the world's leading reproductive medicine journals, researchers have investigated one of the reasons why this happens and have, for the first time, been able to calculate that the proportion of multiple pregnancies after SET is 1.6% and that 1.36% of multiple pregnancies after SET occur as a result of a process called zygotic splitting.
0 kommentar(er)
