Hani, a 37-year-old migrant worker from Cianjur in West Java, was held soon after arriving from Bangkok at Soekarno-Hatta airport around 1:00 am, said airport police chief Ahmad Yusef.
"She didn't look healthy and won't be questioned until she is fit. The woman is now at the airport's health centre," Yusef told AFP.
Police suspect that Hani, who had worked as a domestic helper in Abu Dhabi for four years, secretly gave birth during an Etihad flight from there to Jakarta on Saturday.
Around four hours after take-off she began bleeding, forcing the captain to divert to Bangkok.
"The woman was in economy class but then laid on a business-class seat with an oxygen mask. The captain then announced we should divert to Bangkok," crew member Francesco Calore told AFP.
The flight left for Jakarta around an hour later without the sick woman, who flew home on a later flight.
Ground cleaners in Jakarta found the full-term dead baby wrapped in a plastic bag in a drawer in one of the plane's toilets, Yusef said, adding the cause of death had yet to be determined.
An estimated five million Indonesians work abroad, of whom around 70 percent are female domestic helpers.
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