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| 2-14. MULTI-FETAL PREGNANCIES a. Multi-fetal pregnancy is a pregnancy involving two or more fetuses. b. Twin fetuses may originate several ways (see figure 2-11). (1) Identical twins (monozygotic) originate from the same ovum and are always of the same sex. They share a single placenta. (2) Fraternal twins (dizygotic) originates from two separate ova and sperm and may be of different sexes. They each have their own placenta.
Figure 2-11. Development of twin fetuses. c. Pregnancies involving more than two fetuses (that is, triplets, quadruplets) may occur by either situation. (1) Monozygotic--all will be identical. (2) Multi-zygotic--often associated with fertility drugs in which the ovary matured and released many eggs in the same cycle. |
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