The study, led by epidemiologist Victoria Holt, Ph.D., M.P.H., a member of Fred Hutchinson's Public Health Sciences Division, is the largest case-control study of its kind to examine the link between body-mass index and oral-contraceptive failure. The research was conducted in collaboration with Delia Scholes, Ph.D., a senior investigator at the Center for Health Studies at Group Health Cooperative in Seattle.
"The results of our study represent yet another reason why obesity is a health hazard," Holt said. "Overweight and obese women have a significantly higher risk of getting pregnant while on the pill than women of normal weight, and this translates into a substantial number of unplanned pregnancies." Among 100 women taking oral contraceptives for a year, Holt's study suggests that an additional two to four women will get pregnant due to being overweight or obese.
"This higher risk of pregnancy also translates into a higher number of obesity-related complications of pregnancy, which range from gestational diabetes and high blood pressure to Cesarean delivery," Holt said.
Body-mass index, or BMI, is a measure of body fat based on height and weight. The World Health Organization divides BMI into four categories for both men and women: underweight (18.5 or lower), normal (18.5 to 24.9), overweight (25 to 29.9) and obese (30 or greater). A BMI calculator is available on the National Institutes of Health Web site at http://nhlbisupport.com/bmi/bmicalc.htm
"We found little difference or variation in the risk of contraceptive failure among women who fell
Contact: Kristen Woodward
Fred Hutchinson Cancer Research Center