Banana Muffin wrote...
Well in Sweden teenage pregnancies are virtually nonexistant, make of that what you want.
As for STDs it's a kind of stupid argument as to why sex would be bad for young people as you are as likely to get it when you are adult. Also it has nothing to do with sex itself it's not different from getting other contagious diseases. It's important to know that you can use a condom to prevent STDs in the same way it's important to know that you should wash your hands after you've been to the toilet or to shower, sneeze in your armpit and shower on occation. Even more important is what you eat and that you exercise (sex is good excercise). There are a lot more americans dying of obesity than of STDs
Do they not teach debate in Sweden? They seem to do everything else so well!

STDs are of great importance for adolescents. Adolescents have different brain function from adults that results in generally poor planning and problem-solving skills and impulsivity problems. This leads to more irresponsible sexual conduct when they do have sex. Teens are less likely to use condoms than adults. Additionally, when teens do get STDs, they usually have worse access to healthcare than adults. True, some because they don't want their parents to know they were having sex, but also because they try to address symptoms by visiting Yahoo Answers instead of the doctor. Additionally, many women in the US get screened regularly for cervical cancer and common STDs because their insurance requires an annual exam in order to cover oral contraceptives--if teens are not on contraceptives or obtain them by a different route they're likely to miss this screening.
Most STDs do not kill people, but the most common bacterial STDs, chlamydia and gonorrhea, can lead to sterility if untreated--and these STDs also commonly do not produce symptoms. Teens tend to pass HPV around like it's the common cold, which in most cases does not matter, but can result in cervical cancer. The recommended frequency of Pap smears decreases with age because older women tend to have settled down to a long-term partner, while younger women have more partners, increasing their risk of exposure to HPV. Having sex at an earlier age increases risks of cervical cancer, some of this is probably due to an increased number of partners, but it's thought physiological factors may be involved (perhaps an immature cervix is more prone to colonization by HPV?) HPV vaccination should decrease the prevalence of cervical cancer, but at the moment we don't have a vaccine for all oncogenic strains of HPV.
Condoms do reduce odds of transmitting STDs, but they do not totally prevent them. Some STDs, like HPV and herpes, are not effectively prevented by condom use. I'm personally interested in HIV-1, and odds of transmission for HIV-1 are cut by 80% with consistent condom use--true, a big decrease, but that extra 20% is an extremely significant gap when it comes to a historically terminal disease. And of course if a condom is not used, it can't help at all.
So, yes, if we move the average age of first sexual activity further on, we should see a decrease in STDs in the population, and we should see the cases that do appear being treated more rapidly.
Teen sex is not shockingly awful, but it's also not something to dismiss by saying sex is natural, so it must always be good.