The 26-year-old actress kept touching her bare tummy and looked radiant as the couple relaxed by the pool in Tenerife in the Canary Islands.
Robbie, 30, could hardly keep his hands off the former Brookside star and Hell's Kitchen winner either.
An onlooker told the People: 'They looked so happy and well. Robbie kept rubbing Jennifer's bump.
'He looked like a proud dad already. This is going to be one cherished baby.'
Glowing Jennifer got engaged to the semi-pro boxer last October after a turbulent seven-year relationship with businessman Tony Richardson.