This is the heartwarming moment an orangutan pressed his face against his glass enclosure - to listen to a pregnant woman's baby.

The 46-year-old male ape was transfixed by the heavily pregnant mother-to-be when she visited the Singapore Zoo on July 8.

Footage taken by the woman's husband Ihsahn Mohd shows the Sumatran orangutan named Charlie listening to the sound of the unborn infant's heartbeat.

Ihsahn's wife was 38 weeks pregnant at the time and gave birth a couple of weeks later to a healthy baby.

Ihsahn said: 'An orangutan at the Singapore Zoo came up to my pregnant wife and listened to our baby's heartbeat. It was very moving.

'The male ape is known to like the attention of humans because he was hand-raised when he was younger.'

The Sumatran orangutan is one of the three species of orangutans. They are critically endangered with a population estimated to be around 14,613.

They are found on the Indonesian island of Sumatra where they live in primary lowland tropical forests, including mangrove, riparian forests, and swamp forests.