superfetation

(-fē tās̸hən)

noun

the fertilization of an ovum during a pregnancy already in existence

Origin: ML superfetatio < L superfetatus, pp. of superfetare < super- (see super-) + fetare, to bring forth, impregnate < fetus, fetus

See superfetation in American Heritage Dictionary 4

noun
Formation or development of a second fetus when one is already present in the uterus, occurring normally in some animal species.
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