Sita was the little girl of King Janaka. Be that as it may, as indicated by one of the references in Adbhuta Ramayana, Mandodari was the mother of Sita. It is accepted that Ravana used to store the blood of the apparent multitude of holy people he executed in a huge pot. One of the sages, Gritsamada put away milk got from darbha grass in a pot to rehearse compensation and to have Goddess Lakshmi as his little girl.

 Ravana took a few to get back some composure of the milk pot by sneaking into Gritsamada's home and emptied the milk into his pot of blood. Mandodari got so annoyed by this underhanded demonstration that she chose to end it all by drinking the substance of the pot. 

In the wake of drinking from Ravana's pot, Mandodari didn't pass on. Rather, she got pregnant with Sita. After Sita's introduction to the world, who is one of the manifestations of Goddess Lakshmi, Mandodari left the infant in Kurukshetra, and that is the manner by which King Janaka discovered Sita.