Quite simply, they are worried having to take on a level of resposiblity a child would require, and are like most younger people psychologically (myself included!): We think we are invincible, and are ignorant enough to believe that diseases will go away if we ignore the possiblity of them.

It's possible that they are in a monogamous relationship in which they don't have to necessarily worry about STD's. Therefore pregnancy is at the top of their list, and to some, is scarrier.

Because ignorance is bliss. That is until they find themselves with a lifelong virus like Herpes, or a deadly disease like AIDS, and they have no one to blame but themselves. All women need to value their bodies enough that they don't allow themselves to be used as receptacles for men's bodily fluids . . . Too often the risk is without pleasure for the women. Some hardly know what it takes for them to have an orgasm, they've never explored the possibility of loving themself. Only the men have a ball, or rather give a ball! While the women are left with goo dripping into their panties or onto the sheets, exposing them to even more opportunities for a virus or germs to grab hold. It's not about whether they are in what they believe to be a monogamous relationship. Women need to take better care of themselves and never give in so easily to any kind of unprotected sex. The only person we can totally trust is ourself, yet we play ourselves like fools. If we don't care about our own health and well-being or our bodies, we can't expect anyone else to respect who we are either. It's a sad reality most women don't realize until after they've been used by selfish and uncaring partners, having learned the hard way.

Maybe they already have AIDS and other STDs....what else is there to worry about when you already have both... EDIT: Please leave a comment if you give a bad rating

Because it's not women posting, it's girls. They have undertaken a course of conduct (being sexually active) without fully realizing all the consequences and when they realize that they have put themselves at risk, the first risk they think of is pregnancy. It's like a new driver having an accident with Mom's car and the first thing that they think Mom will think of is the condition of the car, when Mom is probably more concerned with the state of health of her child. It seems like the most immediate consequence, and in the case of pregnancy, it is more immediate, but it's not the most serious, when an unwanted pregnancy can be terminated so easily.

Mainly the worried posters seem to be teenagers. For some reason when we're young we seem to think of ourselves as invincible- how many of you did stupid things as teenagers (walking home alone in the dark, taking drugs, crossing the road without looking...) STD's can take years to develop and we don't have to deal with them until some time in the distant future- whereas pregnancy has to be dealt with in the here and now. Its difficult to convince teenagers that they aren't immortal- its part of human nature. It does hit hard a few years later though- same as I sit here worrying I did myself permanant damage by being stupid enough to smoke for five years. I think it would do some good to send people who are now living with HIV contracted as teenagers into schools to talk about their experience.