A new analysis published Thursday by the Centers for Disease Control and Prevention states that the use of opioid painkillers by pregnant women doubles the risk of birth defects. The March of Dimes, along with the government agency, wrote that “given that many pregnancies are not recognized until well after the first few weeks and half of all U.S. pregnancies are unplanned,” and that birth defects tend to develop in the first few weeks of pregnancy, all women who may become pregnant are at risk. José F. Cordero, MD, MPH, a pediatrician who previously worked at the CDC and current member of the March of Dimes Board of Trustees, asked physicians and other prescribers “not to write prescriptions for opioid-based painkillers for their female patients who may become pregnant without a discussion of the risks and safer alternatives,” according to a media release. CDC found that codeine, hydrocodone and oxycodone were the most frequently prescribed opioids among women in an analysis of 2008 to 2012 prescription claims.