Endometrium A and B are more suitable for fertilization compared to endometrium B. Endometrium A is usually the endometrium in the follicular phase after menstruation and is thinner, while endometrium B is the endometrium close to ovulation and is thicker.
The endometrium can be divided into three types: A, B and C. Type A endometrium, which is around the follicular stage, is generally unsuitable for fertilized egg implantation due to the lower level of estrogen, thinner endometrium and less blood vessels. Type B endometrium, on the other hand, is the endometrium close to ovulation, when the endometrium is thicker and rich in blood vessels, making it more suitable for the fertilized egg or embryo to implant.
Therefore, in order to increase the rate of implantation, it is recommended to have sex during the ovulation period, and to rest in bed for a period of time after sex, so as to facilitate the sperm to enter the uterine cavity more smoothly.