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Review
. 2005 Jan:19 Suppl 1:8-9.
doi: 10.1111/j.1365-3016.2005.00609.x.

Factors influencing twins and zygosity

Gary V D Hankins  1 , George R Saade
Affiliations
Review

Factors influencing twins and zygosity

Gary V D Hankins et al. Paediatr Perinat Epidemiol. 2005 Jan.

Abstract

Zygosity is influenced by many factors. Monozygotic twins occur spontaneously in approximately 1 in 250 births and are felt to increase twofold with ovulation induction techniques. Monozygotic twinning also increases in proportion to the number of blastocysts transferred during in vitro fertilisation. In contrast, dizygotic twinning appears to be influenced by race, genetic factors, maternal age, fertility enhancing drugs, folic acid supplementation, and maternal nutritional status.

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