A world-first study in Perth is helping to unravel why being a mother can cause years of back pain.
University of WA occupational biomechanist and PhD student Adele Stewart says early motherhood causes back pain in up to 90 per cent of women, but it is not known what role back strength and hormones play.
Pregnant women are often told back pain is just part and parcel of motherhood.
"Pain is a complex and personal experience and not always a sign that something is wrong, but the combination of pain and dysfunction often is," Ms Stewart said.
"Pregnant women and new mothers are frequently told 'back pain is part of the journey so accept it' but in reality it could mean an increased risk of injury."
She is testing the theory that the hormone serum relaxin, which helps the ligaments soften in pregnancy but could make the back joints so lax that it creates the potential for injury.
"The hormone is produced in high quantities during pregnancy, particularly in the first half of the pregnancy when the risk of back pain is not considered as great as in late pregnancy," she said.
"It's possible there is a loss of strength and stability and the woman is far more vulnerable to back injury which may get carried through the pregnancy."
Ms Stewart said a weakened lower back increased the risk of injury, a particular issue when it came to looking after children, both at home and in child care.
"We can't effectively limit or treat back pain and disorder until we know more," she said.
Cara Deed is 27 weeks pregnant with no history of back pain but woke up a few months ago in excruciating pain in her lower back.
"I was told it was part of being pregnant," she said.
The study needs women planning to become pregnant, those in the first 12 weeks of their first pregnancy and first-time mothers with a baby aged three to six months.
Healthy women who have never been pregnant are also needed.
For details, email firstname.lastname@example.org .au.