Depending on the species, sharks either lay eggs or give birth to live young. Sharks that lay eggs are oviparous, and sharks that give birth to live young are viviparous. Viviparous sharks are further divided into placental and aplacental categories, meaning the shark pups either have a placenta or not.
Whether the shark pups emerge from an egg sac, known as a mermaid's purse, or from the mother's womb, there is no parental care following birth. In fact, for viviparous sharks, the threat of being consumed by the mother is immediate upon birth. Also, viviparous shark pups may cannibalize their siblings during the gestation period.