Acupuncture and exercise can help relieve pelvic pain during pregnancy, Swedish researchers said on Friday.

About 30 percent of pregnant women suffer pelvic pain, usually in the back. Although doctors are not sure what causes it, they suspect a surge in hormones during pregnancy affects muscles and ligaments.

Women can wear a pelvic belt to relieve the pain and do exercises at home. Stabilising exercises to improve mobility and strength is another therapy.

But researchers at the Institute for the Health of Women and Children, in Gothenburg, Sweden found acupuncture also helps.

“Acupuncture decreases the pain,” Helen Elden, a midwife at the institute, told Reuters.

Elden and her colleagues compared standard treatment, stabilising exercises and acupuncture on 386 pregnant women. Those who received acupuncture and did the exercises for six weeks reported less pain than the others.

The pain scale was also assessed by an independent examiner.

The researchers said acupuncture and stabilising exercises are effective complements to standard treatment for pelvic pain during pregnancy.

“The findings are of particular importance because no previous study has shown such marked treatment effects among pregnant women with well defined pelvic girdle pain,” the researchers said in a report published online by the British Medical Journal.