How could I write an essay about teen pregnancy?

The main difficulty with writing an essay about teen pregnancy is avoiding generalizations and cliches. There are several ways to do this. The first is to narrow your focus to some specific aspect of teen pregnancy. Some possible ways to narrow your topic would include:
Focus on teen pregnancy in one specific city or town.
Look at the relationship between teen pregnancy and poverty.
Consider differences in rates of teen pregnancies among ethnic groups. 
Examine the varying success rates of different programs aimed at reducing teen pregnancy.
Investigate how some politicians' efforts to defund Planned Parenthood and remove or alter the sex education offered in schools affect efforts to reduce teen pregnancy.
Look at the simultaneous popularity and ineffectiveness of abstinence-only programs.
Examine the health or economic impacts of pregnancy at specific ages.
Next, the more research you do, the easier it will be to write your paper. The key is finding reliable sources of information. If you are located in the United States, a good starting point is the Center for Disease Control and Prevention, a government agency that, among other things, collects statistics on public health issues.
https://www.cdc.gov/teenpregnancy/about/

https://www.pewtrusts.org/en/research-and-analysis/blogs/stateline/2015/3/03/racial-and-ethnic-disparities-persist-in-teen-pregnancy-rates