My husband, who is an OB/GYN, and I were on a cruise 10 years ago. The captain asked my husband to see a passanger who had been taken off the ship in St. Lucia. The passanger was 23 weeks pregnant and bleeding. (had been an uncomplicated pregnancy to this point) My husband was shocked when he arrived at the "hospital". He said it was like the hospital scenes in "Gone with the Wind". There was no equipment available to evaluate either the mother or the fetus. Things we take for granted here, Ultasound machines, blood tests, monitors, are non existant. The passanger ended up being flown (by medical transport) to San Juan and then on to Miami. They called us several weeks later to say they had delievered a healthy, yet premature infant.
My guess is Disney limits the gestational age to 24 weeks because with state of the art medical care, a 24 week infant has a chance at survival. Trust me...this type of medical care is not available in the Caribbean.
Having worked in obstertrics for the past 18 years I know that even an uncomplicated pregnancy can get complicated ....