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Monozygotic twins

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Monozygotic twins  (MONOZYGOTIC twins)

Almost confinements there is a single birth1 or single delivery1, but at some there are plural births2, multiple births2 or multiple deliveries2. Two children born during the same confinement are called twins3 and we may distinguish between monozygotic twins4, uniovular twins4 or identical twins4 on one hand, and dizygotic twins5, biovular twins5, fraternal twins5 or non-identical twins5 on the other. Monozygotic multiple births occur when one ovum splits after fertilization; the resulting children must always be of the same sex. Dizygotic multiple births are due to the simultaneous fertilization of two or more ova and the resulting children may be of different sexes.

  • 1. Single births result in one child only, who in medical literature is sometimes called a singleton.
  • 2. The number of infants born in each delivery has been called litter size by some biometricians but in general, this term is reserved tor animals.
    In British official terminology the term maternity is used to denote a confinement resulting in the birth of one or more children; the number of births per maternity may be computed.
  • 3. Where a multiple birth results in three children, these are called triplets, four are called quadruplets and five quintuplets. The terms "twins", "triplets", etc. may be used in different ways. Generally they are used in accordance with the total number of deliveries during a confinement, especially if at least one baby is born alive, e. g. one of a pair of twins may be alive when delivery is complete and the other dead. Occasionally, however, multiple births are classified only in accordance with the number of children born alive.