Though the number of teen pregnancies has been declining across the country over the last two decades, the population of moms who have a second child while still a teenager has remained stubbornly constant for years. Although some doctors won't insert IUDs in teenagers because of concerns that the young women might remove them, studies have shown that's not the case. A study by UTMB, published in the May issue of Obstetrics & Gynecology, showed teen continuation rates are similar to those of women 25 to 44 years old.