After Leto became pregnant with Eileithyia's half-siblings, the twins Artemis and Apollo, her mother Hera kidnapped Eileithyia to prevent the Titaness from giving birth until the rest of the goddesses rescued her. After Artemis midwifed the birth of her own brother Apollo, she came to share the same province of childbirth and midwifery with Eileithyia.
After Zeus lay with Alcmene and she became pregnant with his son Herakles, the king of the gods proclaimed that the next child to be born of the house of his son Perseus, founder-king of Mycenae, would rule the city and the greater region of Argolis, intending for Herakles, born as Perseus' great-grandson, to become king.
Seeking to spite Zeus, Hera had her husband swear on oath to confirm his proclamation, and Eileithyia, having arrived at Alcmene's house in Thebes to help the latter deliver her son, was forced by her mother to delay Herakles' birth. At that same time, Nikippe, wife of Perseus' son Sthenelos, was herself seven months pregnant and Hera arranged for her to give birth first, resulting in her son Eurystheus becoming king while Herakles was effectively robbed of his birthright.
- Reproduction Manipulation: As the Goddess of Childbirth and Midwifery, Eileithyia has absolute control and divine authority over reproduction. As shown in Percy Jackson's Greek Heroes, she is able to freely alter and manipulate the process in which living organisms produce offspring. She delayed Alcmene's delivery of Heracles and accelerated Eurystheus's birth, though this affected the latter's health.
- Eileithyia and Artemis share jurisdiction over childbirth and midwifery.
- Her Egyptian equivalent is Tawaret.