superfetation

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

A second conception some time after a prior one, by which two fetuses of different age exist together in the same female: often used figuratively.

The fetus produced by superfetation; hence, any excrescent growth.

The formation of a fetus at the result of an impregnation occurring after another impregnation but before the birth of the offspring produced by it. This is possible only when there is a double uterus, or where menstruation persists up to the time of the second impregnation.

An excessive accumulation; a superfluous addition.

The formation of a fetus while another fetus is already present in the uterus.

fertilization of a second ovum after a pregnancy has begun; results in two fetuses of different ages in the uterus at the same time