"We knew we had about a 15 to 20-minute transfer time to the hospital but within five minutes of bringing the mother on board we realised we weren't going to make it to the hospital.''
The 40-year-old, who has two children aged five and 10, said of the woman: "She did everything she was asked to do and the father was very supportive.''
The Coastguard received a call from the unnamed mother's doctor at 4.30am, asking about ferry times from Unst as she was in labour.
After a discussion they decided instead to launch the helicopter which landed 90 minutes later and took the woman and her partner on board.
The baby could not wait and was delivered at 6.28am at 300 metres above a small island called Lunna Holm.
Alex Dodge, watch manager at Shetland Coastguard, said: "This is the first time that a baby has been delivered on the Coastguard search and rescue helicopter based at Sumburgh in the Shetland Islands.
"We would like to congratulate the mother and father on the birth of their son, who is reported to be doing well."
- AAP