New research shows that when a pregnant woman works in extreme heat, it can pose a health risk to her foetus.

The study monitored more than 90 subsistence farmers working in rice fields in The Gambia - in direct sun and often high humidity.

Researchers from the London School of Hygiene and Tropical Medicine said the heart rate of each mother's unborn child increased to dangerous levels.

They found the blood flow to the foetus slowed as the mother's placenta was impacted by the heat.

The scientists are calling for more research, with many locations facing rising temperatures.