A question about the show"LOST"...?

How could Benjamin Linus and Danielle Rousseau have had a daughter (Alex), if supposedly women can't have babies on the island without dying?

Danielle was pregnant when she first got to the island, with the team of people on her research vessel.Ben Linus adopted Alex as an infant ( stolen from Rousseau), who only learned about and met her mother several days ago by island time.

Only women who become pregnant on the island die.The women who come to the island pregnant like Claire survive when they give birth.And Danielle's daughter was stolen by Ben's people and Ben adopted her.