The third and fourth generation contraceptive pills expose women to twice as high a risk of blood clots as the second generation pills, a new Danish study said Wednesday. \"We found that contraceptive pills are generally more dangerous than previously believed, and that the difference between the second, and the third and fourth generation, is somewhat larger than we had thought,\" Professor Oejvind Lidegaard of Copenhagen University Hospital, who conducted the study, was quoted by Denmark\'s Information newspaper as saying. Some 370,000 Danish women currently take oral contraceptive pills. Among them, 84 percent take third and fourth generation pills, while just 16 percent take second generation pills. On average, five Danish women between the ages of 15 and 49 die of blood clots every year, with three to four of those deaths attributed to contraceptive pill use. The clots typically occur in legs and lungs. Lidegaard\'s study, which covers users between 15 and 49 years of age, shows that one in 1,000 users of the second generation pills develops blood clots, as opposed to roughly one in every 500 women taking the third and fourth generation pills. \"At the risk of exaggeration, one can say that they are twice as expensive and twice as dangerous,\" Lidegaard said of the latest generation pills. The new study will be published in the British Medical Journal on Wednesday. Previous studies have shown the latest generation pills to be less safe than their second generation predecessor, but Lidegaard\'s study so far provides the most conclusive evidence for this, Information newspaper reported. The third and fourth generation pills are sold in Denmark under brand names such as Yasmin, Yaz and Yasminelle, and comprise the lion\'s share of the market. The latest generation contraceptive pills are aggressively marketed by their manufacturers and protected by patents. They cost more than the older pills whose patents have run out and are often widely produced, Information newspaper said.