In the past years, multiple births have been multiplying at a fast rate. In the U. S in , only In , 33,9 sets of twins were born per 1, births, according to a report on birth data. When it comes to having twins, not all regions are equal.
Recently we looked at the question of how likely a two-child family with a boy is to have another boy or, to the contrary, to also have a girl. Searching for those questions turned up another one of interest involving the gender of a pair of siblings: How do things change when they are twins? Her husband used the same basic model we used in The Other Child : there are four equally-likely possibilities in a two-child family, based on birth order. But Melissa disagrees with this model, because twins are the same age. Is she right?
Twins are two offspring produced by the same pregnancy. In contrast, a fetus that develops alone in the womb is called a singleton , and the general term for one offspring of a multiple birth is multiple. The Yoruba peoples have the highest rate of twinning in the world, at 45—50 twin sets or 90— twins per 1, live births,    possibly because of high consumption of a specific type of yam containing a natural phytoestrogen which may stimulate the ovaries to release an egg from each side. In Central Africa , there are 18—30 twin sets or 36—60 twins per 1, live births.
The majority of twins are fraternal twins twins that look different from one another. Learn more about fraternal twinning, from how they form to how they relate to each other, as well as how they differ from identical twins. Zygotic refers to zygote, the egg fertilized by the sperm that will develop into an embryo and grow into a baby.