What It Is
Experts define normal weight as a BMI (body mass index) of 18.5 to 24.9. Overweight is a BMI between 25 and 29; 30 and over is considered obese. The formula to calculate BMI is a bit complicated: Take your weight in pounds and divide it by your height in inches, squared. Multiply that result by the number 703. Or, for an easier way, plug your height and weight into Conceive’s automatic BMI calculator: BMI Calculator
Who Gets It
About two-thirds of adults in the United States are overweight, and almost one-third are obese, according to NIH. Almost 62 percent of women and slightly over 70 percent of men are overweight.
Studies have shown that women who are overweight – not necessarily obese – experience problems getting or staying pregnant. Overweight men have more difficulty fathering a child.
How It's Diagnosed/Detected
Keeping track of BMI is the best way to know if a few extra pounds here and there may be leading to overweight.
How It Affects Fertility (And Pregnancy)
In women, a low level of circulating estrogen is the brain’s signal to pump out other hormones that prod the release of new eggs from the ovaries. Fat cells produce a weak form of estrogen, so if a woman has too much body fat, the brain can be fooled into thinking that the hormones are all doing their job and the egg-release cycle doesn’t get under way. Excess weight also increases the risk of a condition known as polycystic ovarian syndrome (PCOS), in which many cysts develop from ovarian follicles that fail to release eggs. According to some experts, more than half of women who are 50 pounds overweight are not ovulating normally. The famous Harvard Nurses Health Study found that 25 percent of all ovulation-related infertility may be due to overweight. Gaining weight even into the high-normal range (a BMI of 24 or above) could compromise a woman’s fertility.
Overweight women who do become pregnant are at increased risk of complications such as gestational diabetes and high blood pressure and are more likely to have a cesarean delivery.
A man who is overweight may have too much estrogen in relation to the male hormone testosterone, which can decrease sperm production. Some studies suggest that a BMI higher than 25 can significantly lower sperm count.Treatment
For most people, watching their diet and getting more exercise are the best ways to keep weight under control. For a woman edging toward obesity, losing just 10 pounds could improve ovarian function. Harvard researchers have found that higher weight women can lower their risk of ovulatory-related infertility through regular vigorous exercise. For every hour per week the women exercised, there was a seven percent drop in their risk of problems with ovulation.
Some experts now believe that a woman’s weight may be a factor in up to 10 percent of all infertility cases, and how much a woman weighs in the years before she thinks about having a baby may also make a difference. The good news, according to the American Society for Reproductive Medicine, is that weight loss alone may make it possible for 70 percent of couples to conceive if their infertility is weight-related.
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