A pregnant woman is in hospital and two men have died after going for a swim in a regional NSW river.

The trio, believed to be aged in their 30s, are believed to have entered the Never Never River, north of Bellingen on the NSW mid-north coast, about 6.45pm on Sunday.

They are understood to have began struggling in the water, leading to reports being made to emergency services soon after.

Two man have drowned in the Never Never River, north of Bellingen in NSW.

The pregnant woman was able to be pulled from the river and was treated by paramedics at the scene before being rushed to Coffs Harbour Health Campus in a serious condition.

Paramedics told 7NEWS.com.au she had suffered from shock.

The two men were also retrieved but were tragically pronounced dead despite the best efforts of paramedics.

Another man aged in his 30s who had been submerged in the water was also transported to hospital.

Police have launched an investigation into the death and will prepare a report for the coroner.