Main Page | See live article | Alphabetical index Superfetation (also spelt Superfoetation, based on a false etymology - see fetus) refers to the formation of a fetus while another fetus is already present in the uterus. It is common in some species of animals, but is extremely rare in humans. It can only occur where there are two uteri, or where the menstrual cycle continues through pregnancy. This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License.