Emlyn Culverwell, 29, and his fiancé, Iryna Nohai, 27, originally from the Ukraine, were detained for more than a month in Abu Dhabi.
They were arrested on January 29 when Nohai was taken to hospital with stomach cramps.
A doctor at the Medeor Medical Centre in Yas Mall confirmed that Nohai a Ukrainian national was pregnant, and they were arrested at the hospital.
They faced charges of having sex before marriage – a crime in the United Arab Emirates.
Culverwell and Nohai had spent five years working at Yas Waterworld and lived in Abu Dhabi before their arrest.