How thick should the endometrium be at embryo transfer?
Through many years it was believed that a certain amount of endometrial growth is essential for the success of implantation of an embryo. A thickened endometrium (lining of the womb) provides a site for implantation and is also a source for nourishment of the embryo which is implanting in the first few weeks of pregnancy as the placenta develops.
There has been a large variation in endometrial thickness observed in patients undergoing assisted conception.
There are many studies which suggest a correlation between endometrial thickness, its receptivity to the embryo and report that a certain amount of endometrial thickness is essential for a successful implantation of the embryo. The question that needs to be answered is how thick should the endometrium be for a successful implantation. Multiple studies have been compared and in a study which was done in Israel published in Fertility Study by Kevin Srichter Etal 2007 suggested that the endometrial thickness on the day of HCG trigger increased as the endometrial thickness also continues to increase but, equally important was that the endometrial thickness was only about 6 or 7mm especially when a good quality blastocyst were transferred, pregnancy rates were close to 50%.
Thus, just cancelling an embryo transfer based on a thin endometrium is not warranted and should be analysed on a case to case basis where the endometrium is triple layer and has a good appearance, embryos of good quality would have a similar implantation even though there may be 6-7mm.