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Multilingual Demographic Dictionary, second unified edition, English volume

Monozygotic twins

Multilingual Demographic Dictionary, second unified edition, English vol.
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Monozygotic twins  (MONOZYGOTIC twins)


At most confinements there is a single birth 1 or single delivery 1 but at some there are plural births 2, multiple births 2 or multiple deliveries 2. Two children born during the same confinement are called twins 3 and we may distinguish between monozygotic twins 4, uniovular twins 4 or identical twins 4 on the one hand, and dizygotic twins 5 or biovular twins 5 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.

  • 2. 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 quadruplets, and five quintuplets. The terms "twins", "triplets", etc. are generally used in accordance with the total number of deliveries during a confinement; occasionally, however, multiple births are classified only in accordance with the number of children born alive.

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