What criteria must the lining of the uterus and follicles meet in order to conceive?

　　
　　“What kind of lining and follicles are necessary for pregnancy?
　　Generally speaking, a woman can get pregnant only if her follicles are 18mm-25mm in size and her uterine lining is 8mm-12mm thick.
　　If the follicle is smaller than 18mm, the ability of fertilization is poor, and it is difficult to get pregnant after discharge; if it is larger than 25mm, the follicle is difficult to be discharged, and it is easy to be luteinized, and it is not possible to get pregnant normally.
　　The endometrium is also the same, too thin or too thick is not conducive to the fertilization of the egg, and even if it does, it is prone to miscarriage, fetal arrest, and ultimately lead to infertility.
　　“What is the relationship between endometrium and follicle?
　　The endometrium and the follicle are like the seasons of the year, growing in tandem. The thickness of the endometrium is directly related to the growth and development of the follicle and the changes in estrogen and progesterone levels.

　　Early follicular stage
　　◆ On the 7th to 10th day of the menstrual cycle, when the menstrual period has just been cleared and the follicles in the ovaries start to grow, the endometrium is at the beginning of the proliferative phase, and is about 2 to 4 mm thick.
　　Mid-follicular stage
　　◆ On the 11th to 13th day of the menstrual cycle, as the follicle develops, the estrogen level gradually rises, and the endometrium gradually thickens to a thickness of about 4 to 8 mm.
　　Ovulation day
　　◆ On the 14th day of the menstrual cycle, as the follicle develops at an increased rate, the estrogen rises rapidly and the lining grows faster, to about 9～12mm before the follicle matures and ovulates.
　　Luteal phase
　　◆ On the 15th to 28th day of the menstrual cycle, the thickness of the endometrium increases a little after ovulation under the action of progesterone secreted by the corpus luteum. At this time, if the egg combines with the sperm, the fertilized egg will be deposited here; if it is not conceived, the endometrium will be shed again to form the menstrual flow.