How do women become pregnant naturally?
Before beginning any assisted pregnancy procedure a couple must understand how things happen naturally. This will help you understand why we request certain tests, and how we arrive at an indication of the most suitable treatment.
Women who have regular menstrual cycles (an interval of 28 to 30 days between one and menstruation and the next) normally ovulate around the 14th-15th day of the cycle. On the first day of menstruation, an egg begins to mature inside what we call the follicle, which is easy to visualize on a transvaginal ultrasound scan, and grows to approximately 20 mm.
Below you can see a rare image during laparoscopy of the moment when the egg leaves the ovary.
While the follicle is growing, the egg produces estradiol, which acts on the endometrium, preparing it for pregnancy. Close to the moment when the follicle ruptures (ovulation) the endometrium takes on an aspect that we call 'trilaminar'.
After the egg has left the follicle, the fallopian tube—a permeable movable organ—captures the egg, which then comes into contact with sperm held inside the tube. In other words, the fallopian tube is an essential organ for natural pregnancy to occur
Inside the tube, the spermatozoon penetrates the egg and fertilization occurs.
The embryo that is formed begins to divide, taking from 5 to 7 days, approximately, to reach the uterus (at which stage it is called a blastocyst) and finally implant itself, thus beginning the whole process of pregnancy.
This photograph shows a blastocyst in contact with the endometrium.
Stages within the fallopian tube from capture of the egg until formation of the blastocyst.