Unplanned Pregnancies More Common in Obese Women

Obese women are less likely to use certain types of birth control and more likely to have unintended pregnancies, according to a new study on a French population.

The study, which looked at the impact of obesity on sexual health, found the rate of unplanned pregnancies is four times higher among single obese women than normal weight women under age 30, despite the obese participants being less likely to have been sexually active in the past year.

This high rate of unexpected pregnancy likely reflects a reliance on less effective means of birth control, the researchers say. Obese women were less likely to use oral contraceptives or seek advice about using contraception.

The study was led by Nathalie Bajos of the Institut National de la Santé et de la Recherche Medicale in Paris, and published online today in the British Medical Journal. 

If the findings can be reproduced in other populations, they should be concerning from a public health standpoint, said Dr. Sandy Goldbeck-Wood, an obstetrician and gynecologist at Ipswich Hospital in England, who wrote an editorial about the study in the journal. Obesity during pregnancy is associated with risks for both mother and baby along with increased health care costs, she said.

The exact causes behind the finding are not known, but the reasons are likely complex, involving social, psychological and biological factors, Goldbeck-Wood said.

For instance, it could be that obese women are less likely to use oral contraception for fear of weight gain, a side effect of the pill, the researchers say. Or health care professionals might be hesitant to prescribe this type of contraception for obese women, because it is associated with an increased risk of cardiovascular events, such as heart attacks. Obese women also might be less likely to seek services for contraception, because they have negative feelings about their body fat.

At the end of the day, clinicians must be prepared to discuss sex and weight with their patients, two topics often seen as touchy subjects for physicians, but which have important effects on health and quality of life. "We need to understand more about how obese people feel about their sex lives, and what drives the observed behaviors and attitudes," Goldbeck-Wood said.

The study surveyed 12,364 men and women ages 18 to 69 and living in France in 2006. Of the participants, 3,651 women and 2,725 men were normal weight (BMI between 18.5 and 25), 1,010 women and 1,488 men were overweight (BMI between 25 and 30), and 411 women and 350 men were obese (BMI over 30).

Besides the birth control and pregnancies related findings, the results showed obese women were 30 percent less likely to have had a sexual partner in the last 12 months. Obese women were also five times as likely to have met their partner on the Internet, more likely to have an obese partner, and less likely to view sex as important for personal life balance.

Social pressure, low self-esteem and concerns about body image may help explain these findings, the researchers say.

Obesity also impacted men's sexual health. Obese men were 70 percent less likely to have had more than one sexual partner in the same period and were two and half times more likely to experience erectile dysfunction. Obese men under age 30 were far more likely to have had a sexually transmitted infection. And those ages 30 to 49 with more than one sexual partner were less likely to have used condoms in the past 12 months than normal weight men.

Considering the growing obesity problem in developed countries, the findings warrant attention, the researchers say, particularly those regarding obese women and birth control.

"Any temptation to think that obese women are less sexually active and therefore less in need of effective methods of contraceptive is clearly without foundation," the researchers write.

• Top 10 Surprising Sex Statistics
• The History and Future of Birth Control
• Weight Loss Improves Sex