Fertilization and conception of a baby occur when only one sperm enters the egg and gives rise to an embryo. Once out of the follicle, it takes less than 24 hours for the ovum (female reproductive cell) to reach the fallopian tube, the place where fertilization takes place. Sperm (male reproductive cells) have it more difficult.Therefore, only the most capable sperm will be able to make the journey. Of all of them, only one, the best endowed, will be the one that finally fertilizes the ovum, crossing the wall of the female cell with its head. When sperm and egg meet in the fallopian tube, fertilization occurs.
The new cell thus created already contains all the characteristics of the future baby, from the color of the hair and eyes, to the predisposition to suffer from certain diseases.
The embryo and cell multiplication:
Once sperm and egg are united, the new cell is called an embryo.
After fertilization, the embryo begins to divide. A cell divides into two cells: two cells make four… and so on, in a geometric progression known as cell division. At the same time, the embryo begins to migrate down the fallopian tube toward the uterus. The hormonal changes that took place before the release of the egg affect the lining of the uterus (endometrium), which prepares to host the embryo.
The growth of the embryo in the uterus:
The embryo is detached from its cortex and implants itself in the uterine membrane. That newly implanted embryo begins to produce a hormone called human (hCG).
Resume:
When an egg meets a sperm in the fallopian tubes, fertilization occurs. The resulting daughter cell then begins to divide and travels down to the uterus where it is housed. Pregnancy is the development of the new being from fertilization to delivery. It lasts for nine months. During the first three months the new being is called an embryo. From the third month it is called a fetus. The fetus already has its organs formed at 4 months. At 9 months it measures about 50 cm. and weighs about 3 kg. Then delivery occurs.
