15 Unanswered Lost Questions That Totally Have Explanations
10. Why Can't Women Have Babies On The Island?
In the third season, it's revealed that women can't survive giving birth on the island. Apparently women who conceive on the island have all died during pregnancy. In fact, Juliet, a fertility doctor, was recruited to figure out why this happens. So did viewers ever get an answer to this?
The Explanation: It's heavily implied that the pregnancy issues were a result of "the incident," when in 1977 an enormous amount of electromagnetic energy was released from the core of the island. The incident was also the reason the Swan station was built and why Desmond had to press the button every 108 minutes: this was an attempt to contain the electromagnetic energy. The epilogue confirms that the electromagnetism on the island does indeed interfere with a woman's gestation period.
So it appears the official answer is that women on the island can't survive childbirth due to electromagnetic energy released in 1977. We do see some successful births before that time, with Ethan being born prior to the incident with no complications.
After the incident, though, there was a huge surge in electromagnetism on the island, and being with child became fatal.