When Wendy Swanson started out as a pediatrician eight years ago, it never crossed her mind to bring up the option of intrauterine devices — an insertable form of long-acting contraception — when she had her regular birth-control discussions with teenage patients who were sexually active.But Swanson’s approach changed after a casual conversation with her sister-in-law. This relative wasn’t a doctor, but she worked at the Adolescent Pregnancy Prevention Campaign of North Carolina, and she told Swanson that the devices could be used as a first choice of contraception for teenagers. Now Swanson regularly discusses IUDs, which are more than 99 percent effective, in her Seattle practice.