Superfetation

Part of speech: noun

Definitions

1. The fertilization of an ovum while a woman is already pregnant, resulting in a second conception ; the presence of fetuses of markedly different developmental stages within the uterus at the same time
2. A second pregnancy occurring while another is already underway through the fertilization of another ovum ; the coexistence of multiple fetuses at significantly different stages of maturity in the womb
3. The conception and implantation of a new embryo during an existing pregnancy ; the simultaneous presence of developing offspring that differ substantially in age or development within the uterus

Etymology: Superfetation names the conception of a second embryo while an earlier pregnancy is already underway, a phenomenon documented in some animals such as certain rodents and rabbits. The word traces back to Latin "superfetare," meaning to conceive while already pregnant, built from "super-" ("over" or "upon") and "fetus," the Latin word for offspring or a bringing forth. The sense is literal: a new conception laid over an existing one. Because the Latin verb had this exact biological meaning from the start, the English term has stayed close to its origin rather than drifting into metaphor. Its parts are transparent to anyone who knows that "fetus" entered English from the same Latin root, which is why the word reads as a plain description of the process it names.

Synonyms: superimpregnation