How many sperms make identical twins

Many friends think that twins are the same, whether they are identical twins or fraternal twins. This understanding is wrong. Identical twins are formed by the combination of one sperm and one egg, which then split into two embryos, so the children born have the same appearance and gender. Fraternal twins are formed by the combination of multiple egg cells and multiple sperm.

1 How many sperms are needed to produce identical twins?

Identical twins are conceived from 1 sperm.

Identical twins are formed when the fertilized egg splits and then separates for unknown reasons after fertilization. In fact, the embryo after fertilization is still surrounded by a layer of zona pellucida, and then it will break out of the cocoon. This is the important moment of splitting into identical twins. If the time of breaking through the zona pellucida is different, different results will be produced. When a sperm and egg cell combine to form a fertilized egg, the fertilized egg splits from the same cell mass into two identical, independent fertilized egg cells that can develop into independent individuals in the early stages of pregnancy. These are identical twins, and the two babies are the same in gender, appearance, and all other genetic material. So, identical twins are fertilized by one sperm.

Different situations of identical twin splitting

The important moment of splitting into identical twins, if the time of breaking through the zona pellucida is different, will produce different results, which can be roughly divided into four types:

a. It divides within three days after fertilization, producing two chorionic cavities (also called "trophoblastic membrane") and two amniotic cavities. The best scenario is that the two embryos develop independently without affecting each other.

b. The two membranes separate more than three days and less than eight days after fertilization, forming one chorionic cavity and two amniotic cavities. The embryos may be connected to each other through their placental blood vessels, resulting in a dangerous condition in which the blood of one fetus is passed from one to the other, called "twin-twin transfusion syndrome."

c. If the cleavage occurs more than 8 days after fertilization, only one chorionic cavity and one amniotic cavity will be produced. Because twins are in the same space, their umbilical cords are more likely to get tangled, and the chance of fetal death is relatively increased. d. If the fertilization takes more than 13 days to separate, conjoined twins will be produced.