Couples who are overweight may take longer to achieve pregnancy than partners who are not as overweight, a recent U.S. study suggests.
Previous studies in women are linked to obesity problems to get pregnant. In the current study, neither the male nor the female obesity was only linked to taking a longer time to become pregnant, but when both partners were obese, the couple rose to 59 percent longer to become pregnant than non-obese colleagues.
“If our results are confirmed, fertility specialists want to take couples’ weight status into account when counseling them about the reach of the pregnancy,” said lead study author Rajeshwari Sundaram of the Eunice Kennedy Shriver National Institute of Child Health and Human Development in Bethesda, Maryland.
“The benefits of a healthy weight are well known: obesity increases the risk of diseases such as type 2 diabetes, heart disease and cancer,” Sundaram added by e-mail.
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Sundaram and colleagues focused on the relationship between pregnancy and the body mass index (BMI), a ratio of weight and height. A BMI between 18.5 and 24.9 is considered a healthy weight, while 25 to 29.9 is overweight, 30 or higher is obese and 40 or higher is what is known as morbid obesity. (The National Heart, Lung, and Blood Institute has an online BMI calculator here: http://bit.ly/1D0ZqDv.)
An adult who is 5 feet 9 inches tall and weighs 160 pounds, for example, would have a BMI of 23.6, which is in the healthy range. An obese adults at that height would weigh at least 203 pounds and a BMI of 30 or more.
Researchers categorized individuals into two subgroups: obese class I, with a BMI of 30 to 34.9, obesity class II, with a BMI of 35 or higher.
Overall, 27 percent of women and 41 percent of men with obesity class I or heavier.
Then the researchers compared the average time to conceive for couples where neither partner was obese, which both fell in the obese class II group.
Couples in the obese class II group has a 55% longer to achieve pregnancy than their normal weight peers, the study team calculated.
After accounting for other factors that influence fertility, such as age, smoking status, exercise, and cholesterol levels, obesity class II pairs took 59% longer to get pregnant.
About 40 percent of men and 47 percent of the women had enough of the excess fat around the abdomen potential impact on fertility.
In addition, 60 percent of women and 58 percent of men said that they exercised no more than once per week, the researchers report in Human Reproduction.
Outside the the small size, another limitation of the study is that it is not a controlled experiment designed to determine whether obesity directly causes of infertility, the authors note. It is also aimed at couples in the general population, not the people who are treated for infertility, so the results may not reflect what would happen for all couples trying to conceive, the researchers suggest.
However, in contrast to many other studies of obesity and fertility, the current analysis used height and weight measured by doctors instead of relying on the participants to this information itself, that make the findings more accurate.
Obesity may influence fertility by changes in the hormone levels in both men and women, the conversion of testosterone to estrogen, said Dr. Jeffrey Goldberg, head of the reproductive endocrinology at the Cleveland Clinic in Ohio.
“If you have more fat there is more conversion of testosterone to estrogen,” Goldberg, who was not involved in the study, said.
It is logical that obese couples would take longer to become pregnant because being overweight not only has an effect on fertility in women.
“For women extra weight impairs ovulatory function,” Goldberg said. “For the boys, with a lower testosterone and higher estrogen inhibits the production of sperm and having a lot of fat around the scrotum, fat thighs and fat around the abdomen increases the temperature of the scrotum and that can also have an adverse effect.”