A 36-year-old man has been arrested following an alleged domestic and family violence assault on a pregnant woman in Tennant Creek last night.

Police allege the man assaulted his 29-year-old sister-in-law, punching her to the head and stomach while she was 30 weeks pregnant.

The woman was taken to Tennant Creek Hospital by St John Ambulance about 9:20pm.

The offender was then identified, and NT Police located and arrested him soon after.

He remains in police custody and investigations are continuing.

Anyone with information about the incident is urged to contact police on 131 444 and quote reference number P26162120.

Anonymous reports can be made through Crime Stoppers on 1800 333 000.