The birth of a child is a great happiness in the life of every family, and the appearance of two at once is a double joy. Previously, twins were born with a frequency of 1 time per 80-100 births, but recently, due to the introduction of reproductive technologies, this happens much more often.
In medicine, the development of two or more fetuses in a woman's body is called multiple pregnancy, and children born as a result of it are called twins. Naturally, multiple pregnancies can form in the following scenarios:
- in a woman's ovaries, two eggs simultaneously ripen, which are fertilized by sperm, resulting in two embryos - fraternal twins;
- in the ovaries, one egg with two nuclei matures, and after fertilization, two embryos are formed - identical twins;
- the fertilized egg is divided into 2 independent parts, in each of which the fetus develops - also identical twins.
Fraternal twins are three times more common than identical twins. Each of them has its own placenta, they can be of different sex and are no more similar than ordinary brothers and sisters. Identicals develop in a common placenta, have the same blood group, usually of the same sex and are similar to each other, like two drops of water.
Twins are usually born in families that have twins in different generations. Moreover, hereditary predisposition must be taken into account not only on the maternal, but also on the paternal side. In addition, the older the woman, the higher the likelihood of multiple pregnancies, especially if the birth is not the first.
You can also conceive twins after taking oral contraceptives: a restructuring occurs in the body, as a result of which two or more eggs can mature. In women undergoing treatment for infertility using hormonal stimulation of ovulation, twins are born in 30-40% of cases.
Finally, the main increase in the birth rate of twins is associated with the development of in vitro (artificial) fertilization: the patient is prescribed drugs that stimulate the formation of several eggs (in some cases up to 20), remove them from the ovaries by puncture, fertilize, and then transfer 3-4 embryos into the uterus to increase the likelihood of having at least one baby. Very often, 2-3 of them take root, which, with a successful combination of circumstances, guarantees the family the appearance of twins.
