Women who are overweight or perform heavy lifting or have certain conditions affecting the body's connective tissue may be at increased risk of having weakened pelvic muscles, a new study suggests.

The study, of nearly 5,500 Swedish women, looked at the potential risk factors for pelvic organ prolapse, a disorder in which weakened muscles and supporting tissue allow one or more pelvic organs to drop down and protrude into the vagina.

Some symptoms include pressure in the vagina, and chronic pain in the lower abdomen or lower back.

It's known that childbirth raises a woman's risk of developing prolapse, but the "nonobstetric" risk factors are less clear.

In the current study, reported in the journal Obstetrics & Gynecology, researchers found that women who were overweight or obese were about twice as likely as thinner women to have pelvic organ prolapse.

The risk was similarly elevated among women who regularly performed heavy lifting at work, versus those who did not.

In addition, women with a family history of pelvic organ prolapse or a personal history of varicose veins, hernia or hemorrhoids were also at increased risk. Both of those findings point to an inherent vulnerability, according to Dr. Ann Miedel and her colleagues at the Karolinska Institute in Stockholm.

As they explain, a family history of pelvic organ prolapse suggests a genetic predisposition toward the disorder, while conditions like varicose veins and hemorrhoids indicate that a woman may have a general weakness in her connective tissue.

The findings are based on a one-time survey of 5,489 women ages 30 to 79. Because the study did not follow the women over time, it's not clear whether lifestyle factors — like being overweight and habitual heavy lifting — caused prolapse in some women.

However, Miedel and her colleagues point out, excess weight and heavy lifting put strain on the pelvic floor muscles, and both factors have been linked to prolapse in previous studies.

The researchers also found a heightened prolapse risk among women who reported frequent constipation. However, they note, chronic constipation is also considered a common symptom of prolapse, and it's not clear which problem came first in these women.

Long-term studies, according to Miedel's team, are needed to establish whether these modifiable factors do cause pelvic organ prolapse in some women.