Teenage pregnancy is pregnancy in a female under the age of 20 (when the pregnancy ends). A pregnancy can take place as early as two weeks before menarche (the first menstrual period), which signals the possibility of fertility, but usually occurs after menarche. In healthy, well-nourished girls, menarche normally takes place around the ages 12 or 13. Whether the onset of biological fertility will result in a teenage pregnancy depends on a number of personal and societal 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 younger than 15. 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 utilisation 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. Among OECD developed countries, the United States, United Kingdom and New Zealand have the highest level of teenage pregnancy, while Japan and South Korea have the lowest in 2001. The latest data from the United States shows that the states with the highest teenage birthrate are Mississippi, New Mexico and Arkansas while the states with the lowest teenage birthrate are New Hampshire, Massachusetts and Vermont.