The woman is thought to be just two weeks away from giving birth.
She was rescued by the RNLI boat from Queensferry after getting stuck during an afternoon stroll on Cramond Island in the Firth of Forth at around 4.20pm on Sunday.
She was taken to the mainland and driven to hospital by family to be checked over.
The path across to Cramond Island is completely submerged at high tide.
Coastguards recommend the crossing is only attempted during the two hours either side of low water.
The dramatic rescue took place as the earth was subject to a supermoon, when the full moon is at its closest point to earth – a phenomenon which can cause perigean spring tides, where tides can be slightly higher and lower than normal.
In February, a baby had to be pulled from the sea at Cramond after a young mum pushing a pram lost her footing on the narrow causeway.
The dramatic incident was caught on video.