Mary the Mother of God or a Jewish pregnant teen with a great alibi is thought to be the only human to have experienced a virgin birth.
Parthenogenesis has been observed in certain frogs but never in a human woman who has given birth five times. Republican Gynocologists for Jesus Grand Wizard explained that after extensive examination of Sara Palin's lady parts, they have reached the conclusion that all of her pregnancies and deliveries were miraculous.
None of the children have any y chromosonal material suggesting that Todd must have been sled racing during conception. Sarah's hymen is still intact as well according to G4J hymenologist, Lovey Membrain: "These urchins passed through her womb like light through glass..."
Further evidence of miraculous events seem present with daughter Bristol. Her statutory rapist and boyfriend is by all accounts impotent and limp as a wet noodle.