NEW YORK (Reuters Health) - 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.
A number of studies have shown that excess weight, particularly around the abdomen, is associated with an increased risk of urinary incontinence in women. In addition, weight loss in overweight and obese women has been found to curb their risk of incontinence.
Urinary incontinence is also related to pregnancy itself. Many women have problems with urine leakage during pregnancy, and pregnancy -- particularly with vaginal delivery -- is a risk factor for developing urinary incontinence at some point in a woman's life.
However, it has not been clear whether the amount of weight a woman gains during pregnancy affects her risk of urinary incontinence either before or after childbirth.
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 weight changes after pregnancy, but not during, 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 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 percent reported urinary incontinence during the 30th week of pregnancy; 21 percent 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 percent of women who had gained roughly seven pounds or less.
However, weight gain after the 15th week was not related to the risk of urinary incontinence by the 30th week. And there was no relationship 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 dipped by two percent for every two pounds she 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 after giving birth. Of those women, 18 percent to 19 percent developed incontinence within six months, versus 23 percent 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 that "weight loss postpartum, together with pelvic floor muscle training, may decrease the prevalence of urinary incontinence in women postpartum."
The findings do not mean that excessive weight gain during pregnancy is harmless, however.
Too many pregnancy pounds may raise the risk of certain complications, such as pregnancy-related diabetes, or contribute to excessive growth in the fetus, which could make for a difficult delivery or make a C-section necessary.
In addition, extra pregnancy pounds are often difficult to shed later.
In the U.S., experts recommend that normal-weight women gain between 25 and 35 pounds during pregnancy, while overweight women should put on 15 to 20 pounds, and obese women 11 to 20 pounds.
SOURCE: link.reuters.com/muw73p American Journal of Epidemiology, online August 20, 2010.