NEW YORK (Reuters Health) - Pregnant women who exercise and strengthen their pelvic muscles are less likely to have problems with urine leakage in their third trimester, a new clinical trials finds.

Experts have long recommended that pregnant women do so-called Kegel exercises to strengthen the muscles of the pelvic floor, including the muscles that help control urine flow.

The exercises may help manage urinary incontinence - a common problem in pregnancy - or help prevent it from arising after childbirth.

Still, there have been questions about just how effective Kegel exercises are in preventing incontinence - particularly the fecal variety, according to the researchers on the new study, led by Signe Stafne of the Norwegian University of Science and Technology.

So Stafne's team randomly assigned 855 women in their second trimester to either join a supervised exercise program or stick with routine prenatal care - which included standard advice to do Kegels and written information about them, but not active instruction.

The exercise group had one weekly hour-long session of low-impact aerobic exercise and strength training, including Kegel exercises.

They were also given a home exercise routine to do at least twice a week.

After 12 weeks, when the women were in late pregnancy, 11 percent of the exercisers said they had problems with urine leakage at least once a week. That compared with 19 percent of women in the control group.

The exercise plan seemed to both treat and prevent problems, the researchers report in the British obstetrics journal BJOG.

Of women who already had urinary incontinence at the study's start, 24 percent were having weekly problems by late pregnancy. That was true of 35 percent of women in the comparison group.

And when women started the study incontinence-free, the exercise regimen seemed to help ward off stress incontinence - urine leakage when there's pressure on the bladder - in particular.

Five percent of women in the comparison group developed stress incontinence, versus just one percent of exercisers.

"The results from the present trial indicate that pregnant women should do pelvic floor muscle training to prevent and treat urinary incontinence in late pregnancy," Stafne's team writes.

As for fecal incontinence, the jury is still out, they say.

Overall, three percent of exercisers had that type of incontinence by late pregnancy. That was lower than the rate in the comparison group - at five percent - but the difference was not significant in statistical terms.

Many women in the comparison group were already exercising when they entered the study, and since all were given information on Kegels, the findings suggest that pelvic exercises are more effective if women get "thorough instructions" in how to do them, the researchers say.

Women can often get instruction on the exercises during prenatal classes, if they take them, or they can ask their obstetrician for help.

SOURCE: http://bit.ly/O4LXQa BJOG, online July 17, 2012.