It may not be how much weight a woman gains during pregnancy, but how much she loses afterward, that affects her risk of urinary incontinence after childbirth, a new study suggests.
In the new study, which followed nearly 13,000 Norwegian women during a first-time pregnancy, researchers found only a weak relationship between pregnancy weight gain and the risk of urinary incontinence during pregnancy. And there was no link between pregnancy pounds and the odds of incontinence six months after delivery.
The findings were surprising, according to lead researcher Stian Langeland Wesnes, of the University of Bergen in Norway.
"For decades," he told Reuters Health by e-mail, "obstetricians have assumed that weight gain during pregnancy to a large degree could explain the peak in urinary incontinence during pregnancy, but scientific proof of the hypothesis has been lacking."
The new findings, Wesnes said, suggest that factors other than extra weight trigger incontinence during pregnancy.
On the other hand, the study found, women who shed more pounds after childbirth had a lower risk of incontinence six months after giving birth, while weight gain after delivery was linked to an increased risk.
Exactly why postpartum weight changes, but not changes during pregnancy, were related to incontinence risk is not clear, according to Wesnes.
One possibility, he and his colleagues speculate, is that the type of weight gain matters. For non-pregnant women, body fat is the main contributor to weight gain; during pregnancy, much of the excess weight is due to the fetus, placenta and increased body fluids.
So there may, for example, be something about body fat -- possibly alterations in hormone levels -- that affects the risk of urinary incontinence, Wesnes noted. But this study, he said, cannot answer those questions.
The study, published online August 20th in the American Journal of Epidemiology, included 12,679 women who completed questionnaires during their 15th and 30th weeks of pregnancy and six months after giving birth.
Overall, 40% reported urinary incontinence during the 30th week of pregnancy; 21% reported a new problem with urine leakage six months after giving birth.
Women who reported gaining a relatively high amount of weight in the first 15 weeks of pregnancy (about 15 pounds or more) did have a somewhat higher risk of incontinence by the 30th week. Forty-five percent reported the problem, versus 38% of women who gained roughly seven pounds or less.
But weight gain after the 15th week was not related to the risk of urinary incontinence by the 30th week. And there was no link between pregnancy pounds and the odds of incontinence six months after childbirth.
In contrast, the study found, among women who had incontinence during pregnancy, the odds of still having the problem six months after delivery fell by 2% for every two pounds lost after giving birth.
Similarly, among women who were continent during pregnancy, those who lost at least 31 pounds from delivery onward were less likely to develop urinary incontinence. Of those women, roughly 19% developed incontinence within six months, versus 23% of women who lost fewer pregnancy pounds.
Wesnes noted that Kegel exercises, which train the muscles of the pelvic floor, are the usual tactic for managing urinary incontinence that develops during pregnancy, and for preventing it from arising afterward.
But, he said, the current findings suggest "weight loss postpartum, together with pelvic floor muscle training, may decrease the prevalence of urinary incontinence in women postpartum."
Am J Epidemiol. Posted online August 20, 2010 Amy Norton Medscape
J. Kyle Mathews, MD
Plano OB Gyn Associates
Plano Urogynecology Associates