Teenage pregnancy is a pregnancy of a female under the age of 20 when the pregnancy ends. It generally refers to a female who is unmarried and usually refers to an unplanned pregnancy. A pregnancy can take place at any time after puberty, with menarche (first menstrual period) normally taking place around the ages 12 or 13, and being the stage at which a female becomes potentially fertile. Teenage pregnancy depends on a number of societal and personal factors. Teenage pregnancy rates vary between countries because of differences in levels of sexual activity, general sex education provided and access to affordable contraceptive options. Worldwide, teenage pregnancy rates range from 143 per 1000 in some sub-Saharan African countries to 2.9 per 1000 in South Korea.
Pregnant teenagers face many of the same obstetrics issues as women in their 20s and 30s. There are however, additional medical concerns for mothers age 14 or younger. For mothers between 15 and 19, risks are associated more with socioeconomic factors than with the biological effects of age. However research has shown that the risk of low birth weight is connected to the biological age itself, as it was observed in teen births even after controlling for other risk factors (such as utilization of antenatal care etc.). In developed countries, teenage pregnancies are associated with many social issues, including lower educational levels, higher rates of poverty, and other poorer "life outcomes" in children of teenage mothers. Teenage pregnancy in developed countries is usually outside of marriage, and carries a social stigma in many communities and cultures. Many studies and campaigns have attempted to uncover the causes and limit the numbers of teenage pregnancies. In other countries and cultures, particularly in the developing world, teenage pregnancy is usually within marriage and does not involve a social stigma.[8] Among OECD developed countries, the United States and United Kingdom have the highest level of teenage pregnancy, while Japan and South Korea have the lowest.