What is the effect of having sex at 16 years old for a girl?

It’s very rarely the sex that negatively effects 16–year old teen girls that choose to be active in this way. It’s almost always the sexism (misogyny) that causes the problems.

If they do the very same things that 16-year old teen boys would be congratulated for, they can unfortunately expect a shit storm of slut-shaming, fear mongering, double standards, and concern trolling.

If you just have to show your “concern,” then make sure all teens enjoy the benefit of your help (STI screenings, fact-based sex education, teaching and modeling consent, ready access to reproductive health services and contraceptives and protection, etc.), not just the girls.