The most common types of multiple births are twins. Twins are categorized into different groups. The two most common types of twins are fraternal and identical.

Fraternal twins are a result of two eggs and two sperm (Segal 4). Twins can be conceived at different times when there are two separate sperm. The tendency to conceive fraternal twins seems to be heredity. Some studies show higher incidence where there is a history of twins on the mother’s side of the family. Fraternal twins can be boy/girl, girl/girl, or boy/boy. Opposite sex twins make up one-third of the twin population, about one in 240 births (Wolner 32). Boy/girl twins develop as differently as single birth children from the time of conception. Fraternal twins can be conceived at the same time, but their birthdays can be days, weeks or even months apart (Segal 37).

The second most common type of twins is ident

Some topics in this essay:
Siam Rugh, Gonal Follistim, , University Minnesota, Vaughan16 Fraternal, National Statistics, identical twins, conjoined twins, multiple births, fraternal twins, fertility drugs, triplets born, twins raised, twins reared, Chang Eng, twins identical twins, times die, identical twins usually, fraternal quadruplets, identical twins reared, apart identical twins, triplets born egg,