By fertilization we mean the fusion of female and male reproductive cells (egg and sperm) to form a zygote (embryo, fertilized egg). The second name for fertilization is conception.
Obviously, for successful conception in a natural way, a mature egg and a full-fledged sperm must meet in the woman’s reproductive organs. The egg is ready for fertilization only 24 hours after ovulation. Sperm are a little more tenacious - some of them can retain the ability to fertilize for three days or more.
The period when successful conception can occur is called the fertile window. Usually this is 1-2 days before ovulation and 1 day after it. It is at this time that unprotected sexual intercourse is most likely to lead to pregnancy.
Fertilization occurs in the part of the tube farthest from the uterus.
For the meeting of the female and male reproductive cells to take place, the woman’s reproductive tract must be passable, and the sperm must have sufficient vitality and mobility.
Another serious obstacle to fertilization is the dense shell of the egg. Spermatozoa contain special enzymes that can destroy it, but sperm alone cannot do this task. This means that a sufficient number of male reproductive cells must reach the egg so that only one of them can penetrate the egg. After fertilization has taken place, they speak of the onset of biochemical pregnancy.