Modern contraceptives have radically changed women 's lives , but they are not risk free . A new study out of the journal of Obstetrics and Gynecology finds the levonorgestrel-releasing intrauterine system ( LNG-IUS ) or progesterone-releasing IUD , may be associated with a higher than expected incidence of breast cancer . This form of IUD was originally developed as a contraceptive , but later was also used as a treatment for women who suffer from heavy periods ( menorrhagia ) as well as endometriosis and chronic pelvic pain . Levonorgestrel is a synthetic progesterone , which is a hormone that 's naturally produced in a woman 's body . It regulates ovulation . The hormone causes changes to the uterine lining and mucus in the cervix which makes it harder for sperm to reach the uterus , therefore making it more difficult to conceive . Because it strengthens the uterine lining , it helps cut down on heavy bleeding . Levonorgestrel is also the hormone used in the Plan B contraceptive , better known as the morning after pill . In this study , Finnish researchers from the Department of Obstetrics and Gynecology at the Hyvinkää Hospital in Hyvinkää , Finland , wanted to examine the association between premenopausal use of the LNG-IUS and cancer rates , especially when it came to endometrial adenocarcinoma ( cancer of the uterine wall ) . The study followed more than 93,000 Finnish women between the ages of 30 and 49 . All of the subjects were using the hormone-releasing IUD to treat their heavy periods from 1994 to 2007 . At that time , up to 60 % of all LNG-IUSs sold in Finland were used for heavy periods and not for contraception . Investigators found that over time , the device did not significantly raise the risk of uterine cancer or ovarian , pancreatic and lung cancers . But researchers did see a spike in the number of breast cancer cases , especially in women between the ages of 45-49 , compared to women in the general population who were not using this particular IUD . `` The number of diagnosed new breast cancer cases among Finnish women who used LNG-IUS for menorrhagia was 19 % higher than in Finnish general population , '' said Dr. Tuuli Soini , the lead author of the study . However , the research does not say that this type of IUD causes breast cancer . Soini also adds `` one limitation of our study was that women suffering from heavy menstruation may in fact represent a selected group of women who may have other risk factors for cancer , such as factors related to lifestyle , genetic factors , just to name a few . '' According to Soini , this study is the first linking premenopausal LNG-IUS use and breast cancer . Two earlier studies did not reveal an increased cancer risk , according to the study . For physicians , this research is a new piece of information they can pass on to those patients . `` It 's a great reminder that we need to weigh the benefits of some of these methods against the risks , '' said Dr. Angela Marshall , director of Comprehensive Women 's Health in Silver Spring , Maryland . `` We need to educate our patients , because many of these therapies may work , but some could have serious side effects . Women need to be told . Then it 's up to the patient , along with a doctor 's guidance , to make the decision . '' The study authors agree . `` LNG-IUS use seemed to protect against endometrial cancer , which is a common cancer type steadily increasing in the population , '' said Soini . `` We are still convinced LNG-IUS is the best treatment modality for heavy menstrual bleeding , a common health problem affecting the quality of life of a large proportion of female population overall . We certainly hesitate to recommend any change of the clinical menorrhagia management guidelines . '' Soini also stressed , `` However , health benefits and health risks should be carefully taken into account while counseling menorrhagia patients , in relation to any hormonal or surgical therapy . ''
Study of Finnish women using progesterone-releasing IUD found higher instance of breast cancer . The women were using the IUD to help with their heavy periods . Comment: