This question is an exact duplicate of:
In Ramayana and Mahabharata few well known characters are not born from Womb. Most of all unusual births. Few Examples Here: Lord Rama and his 3 brothers (born after eating Dessert) Karna and Pandavas (Mantra), Kauravas (Lump of Flesh) and Drona (Born in a Vessel), Is it true. If yes, How is it possible?
Does it happen only once in period of Ramayana and Mahabharata, are there are any signs in Kaliyuga?