Superfetation is a rare phenomenon that occurs when a second pregnancy happens alongside an existing one. It involves the fertilization and implantation of a second ovum (egg) in the womb while an initial pregnancy is already underway. This results in the simultaneous occurrence of more than one stage of developing offspring in the same animal, including humans and other mammals. While superfetation is more commonly observed in animals, there have been reported cases in humans, although it is extremely rare. The rarity of superfetation in humans is attributed to the bodys natural barriers that prevent a new pregnancy while a fertilized egg is already growing inside the uterus. In humans, superfetation is so uncommon that there are only about 10 confirmed cases worldwide. The phenomenon is often observed in other animals, and it is more common in species such as rodents, small mammals, and fish. Superfetation may be suspected when a doctor notices that twin fetuses are growing at different rates in the womb, a condition known as growth discordance.
In conclusion, superfetation is a rare occurrence in which a second pregnancy happens alongside an existing one, involving the fertilization and implantation of a second ovum in the womb. While it is more commonly observed in animals, there have been reported cases in humans, although it is extremely rare. The phenomenon is often associated with growth discordance in twin fetuses and is more common in species such as rodents, small mammals, and fish.
