Teenage pregnancy is a situation which involves female adolescents, usually less than 20 years old. But sometimes preteens (people under 13) can become pregnant as well. The fact that teenagers become pregnant is related to many factors. These are related to the specific situation of the teenager, and the group that she interacts with. The rates of teenage pregnancy vary from country to country and are related to differences of sexual activities, the general sex education and contraceptives being available. Teen pregnancy will sometimes involve low birth weight. Social matters also play a role: Often, the teenager grew up in poverty. She also often has a lower level of general education. Pregnancy in teenagers in the developed world usually occurs outside of marriage. The lowest levels of teenage pregnancy are in Japan and South Korea. Teenage pregnancies are common among Romani people. Bulgaria and Romania have the highest teenage pregnancy rate in Europe.