Women who want to stave off aches and pains in pregnancy should exercise regularly before they conceive, experts say.
High-impact activities such as jogging, ball games and aerobics may be the most beneficial for preventing pelvic pain, which is thought to affect up to one in five pregnant women.
Exercising between three and five times a week before trying for a baby helped cut pelvic pain in pregnancy by 14 per cent, according to the study in the British Journal of Sports Medicine.
Pregnancy pelvic pain - frequently called pelvic girdle pain - occurs when the body makes way for a developing baby.
It is likely to be caused by a combination of factors, including the joints in the pelvis moving unevenly and changes to the way muscles support the joints in the pelvis.
It can occur anywhere in the pelvis, and can lead to some women struggling to walk or sleep due to excruciating pain.
Up to one in five women suffer from pelvic pain during pregnancy.
In the latest study, researchers, including from the Norwegian Institute of Public Health, examined data from women taking part in the Norwegian Mother and Child Cohort Study.
Some 4069 women reported pelvic girdle pain in pregnancy. Of these, 12.5 per cent had not exercised before getting pregnant.
Compared with non-exercisers, women who exercised three to five times a week pre-pregnancy had a 14 per cent lower risk of developing pelvic girdle pain in pregnancy.
The researchers said: "Taking part in high-impact exercises such as running, jogging, orienteering, ball games, netball games and high-impact aerobics were associated with less risk of pelvic girdle pain."
They concluded: "Women who exercise regularly and engage in high-impact exercises before the first pregnancy may have a reduced risk of pelvic girdle pain in pregnancy."
All the women had been asked during the 17th week of pregnancy to describe the type and frequency of any exercise they undertook in the three months before falling pregnant.
When in their 30th week of pregnancy, they were asked about the frequency and intensity of pelvic pain.
The average age of the women was 38, but age range was from 14 to 46.
Those who reported pelvic girdle pain were more likely to smoke, be overweight, young (under 25) and to have a history of depression and low back pain.
But even after taking into account these factors, there was still a clear 14 per cent reduction in the risk of developing pelvic girdle pain by week 30 among exercisers.
There was no extra benefit for those women who exercised more than five times a week.