Alphabetic Guide to Child Care - Twins and triplets

Twins and Triplets

Multiple births may be identical —that is, the result of the splitting of a single egg fertilized by a single sperm—or they may be fraternal , which means that they developed from different eggs fertilized by different sperm. Most multiple births are fraternal; except for their birthdays, most twins and triplets are no more alike than other brothers and sisters of the same family.

Although there is no ready explanation for the occurrence of multiple births, the tendency is thought to be genetically determined through the mother. Twins occur about once in every 80 births; triplets and higher order multiples much less frequently, although the number of triplets born to American women has quadrupled since 1971. Multiple births are much more likely to be premature than single births. They often require special medical attention after delivery.