Does women’s age, weight, body mass index (BMI) and other factors affect the use and effectiveness of oral contraceptive pills? To try to answer this, data from 59,510 European women in the European Active Surveillance Study on Oral Contraceptives have been analysed by a team of US and German researchers. They matched these data with women’s reports of unplanned pregnancies during pill use, confirmed in follow up interviews. The researchers found there was little, if any, variation in the pill’s effectiveness for women based on their weight or BMI. Oral contraceptive failures were, however, less common in women aged over 30 and in women who had used the pill for longer durations. The report in the September 2009 American Journal of Obstetrics and Gynecology found the European women using oral contraceptives had a high level of effectiveness with typical use. One exception was that oral contraceptives containing chlormadinone acetate (not available in New Zealand) were significantly less effective in women over 75kg or a BMI above 30.