How Does Pregnancy Occur Naturally

Ovaries are the main organs that contain the female sexual (reproductive) cells. They contain millions of female reproductive cells that are too small to be seen by the naked eye or even by an ultrasonographic examination. These cells have a predetermined life course, acquiring different sizes and characteristics at each stage of their lifespan. The female eggs in the ovaries are referred as “follicles”.

In the ovaries (right and left)  of a healthy woman, approximately 8-10 eggs (oocytes) evolve into antral follicles in the first three days of the menstruation so that they can be fertilized. Antral follicles are 2-7 mm in size and their size can be measured via ultrasound imaging. For these eggs to mature, the brain starts to secrete a hormone called FSH and the antral follicles start growing under the effect of this hormone. Of these follicles, one grows faster and inhibits the secretion of this hormone from the brain, preventing the other antral follicles from further maturation. However; the first one will continue its maturation, containing the egg (oocyte), which is your dominant female sex cell selected for ovulation. On one hand, the selected egg of yours secretes the hormones to prepare the internal lining of the uterus, increasing its thickness to make it appropriate for the embryo to grow. On the other hand, it continues to grow predeterminedly, increasing its size by 1-1.5 mm per day. Finally, this selected follicle cracks (ovulation) in the period between the 13th to 15th days of menstruation, releasing the female germ cell inside. This is actually a kind of a small explosion, propelling the germ cell towards the uterine tube. The hairy structures at the end of the tube catch the egg and take it inside.

The egg inside starts travelling ahead by the movements of the hair-like soft brooms in the tube. Unfortunately, the life expectancy of this egg is only 1 day. When the couple have sexual intercourse, the male reproductive cells (sperms ) are left at the entrance (cervix) of the uterus. Then, they will start to swim forward along their ways using their own energies. First, they will reach the cervical canal, secondly, they will reach the uterine cavity, and then, they will proceed in the tube to fertilize (fertilization) the female germ cell (the egg or the oocyte); which will survive only a day.

After a few days, the fertilized egg moves again with the movements of the hairs in the uterine tubes and finally falls into the uterine cavity. In the meantime, the inner lining of the uterine cavity  have become pretty suitable for the implantation of the fertilized egg. Therefore; after falling inside the uterine cavity, the fertilized egg adheres to the inner layer of the uterus and settles down there, extending deeply and connecting with the uterine blood vessels by secreting several substances itself (implantation). At that time, your blood test for pregnancy (beta-hCG) becomes positive.