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(HealthNewsDigest.com) – Even if you and your partner are healthy, being severely overweight affects the frequency of intercourse. This alone, reduces the chance of pregnancy. It is estimated that excess weight decreases the possibility of pregnancy by 30%. This means 30 out of every 100 overweight women will have trouble achieving a healthy pregnancy and carrying a baby to term.
The relationship between weighing too much and infertility is complicated. It affects both men and women in numerous ways and it impacts on both natural and assisted fertilization.
Over 40 studies have examined the link between overweight and pregnancy. These studies show that obese men and women are less likely to have their first child by age 47 and they are far more likely to have only one child. This may be due in part to the fact that fewer obese individuals get married.
For men, being too heavy affects sexual function in general, reducing the frequency of intercourse and increasing the frequency of erectile dysfunction. Fat tissue alters the male hormone profile creating an overall feminising effect. Heavy men have poor semen quality because the sperm’s genetic integrity has been altered.
For women, being too heavy affects pregnancy at every level. The general health of one’s ovaries may be less than ideal. Overweight reduces the likelihood of regular ovulation and the quality of the eggs released. The process of sperm-egg fertilization and the successful implantation of the fertilized egg are less likely to be successful for overweight couples. Weight affects both the success rate of natural fertility and the artificial insemination. And, sadly, overweight women are at greater risk for miscarriage.
Some experts have suggested that IVF (invitro fertilization) should not be tried on women with very high BMIs (body mass index) because the success rate is so low. A BMI of 18.5 to 24.9 is considered normal. BMI is based on your height and weight, and it is used to estimate your health risk. As BMI goes up your risk of illness goes up. Women with BMIs greater than 25 are 29% less likely to get pregnant following IVF. They also require higher drug doses to induce fertilization and are at higher risk of miscarriage. All this adds to the disappointment already faced by couples who are having difficulty conceiving.
Some intriguing, recent evidence showed that the negative effects of being overweight were more pronounced in younger women and less so for women in their mid-30s. This is actually good news. If younger, overweight women lost weight their chances of conceiving may improve.
We now know that fat tissue, which we once thought was inactive, is actually a highly active metabolic and endocrine organ. This means that carrying around extra fat causes changes in the production and function of reproductive hormones. Obesity is also an inflammatory condition which can negatively affect fertility as well.
This leads to the obvious question of what happens to fertility rates when an overweight person loses weight. Some studies have addressed this question but none of the studies were rigorously controlled trials. That means we can consider the results but they are not absolute enough to use to make general recommendations to the public at large. Nonetheless the results are intriguing and they all point toward weight loss having a positive effect on fertility rates.
One study showed that sperm quality improved for men who lost weight. For women who went on a six month diet and exercise program, losing on average about 14 pounds, 90% started ovulating and 85% became pregnant naturally or with assistance. In another study lasting 32 weeks, where women lost over 20 pounds, 80% had improved menstrual function and their chances of getting pregnant improved by 29%. In a comprehensive review of studies on weight loss surgery most women had improved fertility after the procedure.
A word of caution is needed about weight loss. Most women need a certain body mass to successfully carry a pregnancy to term. Severe weight loss is not desirable and losing too much weight or losing it too fast can also impact on conceiving.
Dutch researchers are currently studying a large group of overweight women with fertility issues to see if lifestyle changes can improve their chances of a successful pregnancy. The outcome of this study may provide some important evidence to help overweight women who are having trouble getting pregnant.
How much a person weighs is clearly an issue in pregnancy. Perhaps it should be one of the first issues considered by the doctor and patient when a couple is having difficulty conceiving. For some, a program of exercise and healthy eating may be the only prescription they need for success.
© NRH Nutrition Consultants, Inc.
Jo-Ann Heslin, MA, RD, CDN is a registered dietitian and the author of the nutrition counter series for Pocket Books with 12 current titles and sales in excess of 8 million books. The books are widely available at your local or on-line bookseller.
Current titles include:
The Calorie Counter, 5th Ed., 2010
The Ultimate Carbohydrate Counter, 3rd Ed., 2010
The Complete Food Counter, 3rd ed., 2009
The Fat Counter, 7th ed., 2009
The Healthy Wholefoods Counter, 2008
The Cholesterol Counter, 7th Ed., 2008
The Diabetes Carbohydrate and Calorie Counter, 3rd Ed., 2007
For more information on Jo-Ann and her books, go to The Nutrition Experts
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