The first thing Don't do it again

The next thing you want to do is look into Emergency Contraceptive. You can get more info at that node, but if used with in 72 hours or so after the sex, it can reduce the chance of pregnancy by up to 70%. Call 888-NOT2-LAT(E) or look in the yellow pages for Planned Parenthood.

Get tested for STDs: look in the yellow pages for a local anonymous clinic or talk to your doctor.

After two weeks you can get a pregnancy test. Do so. If it turns up positive, you should take another, just in case, and start to think about adoption and abortion. You might also look into RU-486, an abortion pill, newly legalized in the USA.You probably aren't mature enough to take care of a kid, really very few people are.

Get condoms and the pill for next time.

Or...

Snuggle closely to the one person you truly love and have chosen to give this gift to. Think warm thoughts about the pitter patter of little feet you've longed to have for years. Sigh uncontrollably. Memorize every detail of your partner, the bed, the room, the lighting, the sounds you hear... Kiss ever so slowly Slowly and almost unconsciously touch every bit of your partner Breath together Stare into each others eyes and discover that you don't really need words. Make cute and endearing small talk about each others lives, idiosyncrasies, unique physical features privy to only you, or anything really. Fall asleep more contented that ever before.

note to the youth of our nation: this node does not imply that sex is good

All of these can happen at any age to any couple. The most important factor is to get information about the options available as soon as possible. Find someone you trust and discuss it with them. It could be a friend who has been through similar circumstances. Trusted parents or family member, neighbors, teachers or school counselor are good places to go to as well. Carefully choose whom you are going to share this with.

In the US a doctor must prescribe ECPs. Many health clinics also provide them. Anything that you tell either a doctor or a counselor is in strictest confidence and will not be discussed with anyone else without your permission. This includes parents, other people in your family, teachers, doctors, and social workers.

Emergency contraception is not birth control. There are other safer and effective methods of birth control that women can use on a regular basis to prevent pregnancy. Emergency contraception keeps a woman from getting pregnant by stopping ovulation, or stopping the ovaries from releasing eggs that can be fertilized. It can also prevent fertilization by keeping the egg from being fertilized by the sperm. And lastly it can prevent implantation, or it stops a fertilized egg from attaching itself to the wall of the uterus.

One type of emergency contraception is often called the morning after pill. This is mistaken because emergency contraceptives are never taken as one pill, the "morning after." They are taken in two doses, 12 hours apart. They work best if taken within 72 hours of unprotected sex. Basically the pills are higher doses of hormones than those contained in birth control pills. Some kinds of emergency contraceptives can have only one hormone, progestin, or can have two hormones, estrogen and progestin. If a woman can't take estrogen or is breastfeeding, she can use progestin-only emergency contraceptives. It may cause very severe mood swings and the taker is going to be a bit rattled. Some women have nausea and vomiting after taking them and there is a prescription medication that will help control the nausea. It's important to keep taking the pills even if there is severe nausea. If the course of pills are not all taken the pregnancy may not be prevented. After taking the contraceptives the following menstruation may come sooner or later than usual. Blood flow also may be different - heavier, lighter, or more spotty than normal. It's imperative to use another method of birth control if there is to be sex any time before the next period starts.

The other method is the insertion of an Intra Uterine Device or IUD. This can be done in a doctor's office but you will need a ride home afterwards. Neither one can prevent STD's nor cause abortions, however, both can prevent the implantation of a fertilized egg.

Emergency contraception will not work if pregnancy has already occurred. It will also not work if there is an ectopic pregnancy. This happenes when the fertilized egg begins to grow outside of the uterus. It's also an extremely serious condition that can be fatal. Symptoms of an ectopic pregnancy usually include extreme pain on one or both sides of the lower abdomen, spotting blood, and feeling dizzy or faint. If you think you have an ectopic pregnancy, go to an emergency room right away.

Many women and couples wonder is emergency contraception is an abortion? No. It's a form of pregnancy prevention. The "abortion pills" Mifeprex (mifepristone) also called RU-486 work after a pregnancy has occurred. Or after a fertilized egg attaches to the wall of the uterus. These pills cause the uterus to expel the egg, ending the pregnancy.

For some women as well as couples emergency contraceptives can be a moral dilemma that could affect them the rest of their lives. Seeking the counsel of a trusted and experienced member of your faith can be invaluable when it comes to making a tough decision. While some churches judge and condemn this practice others can be afraid to even discuss it. Know that many of the faithful have walked this path. Don't be afraid or ashamed to ask the doctor or nurse to help you. They should be able to put you in touch with a pastor or priest who can offer some well informed support.

Please be aware that there are rare times when others need to be involved, but this is only when a doctor or counselor feels that a young girl's life is seriously at risk. When this is the case, they will always discuss it with you first.

Many thanks to icicle and BlueDragon for their suggestions and additional important information.

Sources:

National Women's Health Information Center :
http://www.4woman.gov/faq/econtracep.htm

Professional experience.

Snuggling up closely to the one person you truly love and have chosen to make a parent is wonderful advice. You should, nevertheless ask your partner before having unprotected intercourse as whether he wants this special gift at this very moment. I assume that this is advice that should be not only given to the female population of the internet, but also to the blokes.

Ask yourself:

• Will you be able to provide for your child and have someone share the burden of looking after that bundle of joy when you will have to study for your exams?
• Will he be happy to find a job to finance you and your child or will you be the provider?
• Will your parents will be happy to be grandparents and babysit while you're clubbing?

Just do me a favour. Think first. Use contraception.

. . . and now, one for the guys . . .

Discuss it with her as soon as possible.

Do not blame her. You had as much responsibility as she did.

Offer to pay for the doctor visit and morning-after pill if she wants to go that route. If feasible, offer to go with her. The same for abortion if it takes her longer than 120 hours* to make a decision. However, make sure not to suggest either option until she's had a chance to say what she thinks. It looks bad if you seem to be pressuring her.

She may not be pregnant, of course, but if she is, you're a part of it too.

If she's carrying to term—even if she's then putting the child up for adoption—tell her you'll help out in any way you can that she wants. You then have to do this, of course. That can include money, emotional support, helping her through whatever flak she may get for getting knocked up out of wedlock, accompanying her to doctor visits, looking after her health, and other things.

If she's raising the baby, decide what level of participation you're comfortable with. At the very least, offer reasonable (or generous) child support. If her idea of reasonable is more than yours but less than the court's, you'll regret not doing this.

In this day and age you're no longer required to offer to marry her, but you can. Bear in mind that she's unlikely to think the offer is motivated entirely by love alone. However, that should certainly be the major factor. In other words, don't propose unless you were at least open to the idea before this whole mess.

If you're not living together, now may be the time—with the same caveats as for marriage. In any case, you should be willing to be a full participant in parenting, or at least as much so as you can tolerate.

She may want more than you're initially willing to give. Discuss this rationally—no "you're ruining my life, bitch!" Be prepared to compromise. Do not suggest abortion.

Be prepared, too, for her to go to the other extreme: she may now want you out of her life entirely. This will be painful, but it's as caddish to force your presence on someone who doesn't want it as it is to withdraw from someone who needs you.

There is also the matter of STIs. Transmission is more likely than pregnancy on a per-partner basis, although fertile women outnumber infected women. Here again, it's important not to blame—she probably did not set out to infect you, and you're as capable of taking precautions as she is. She may, in fact, be unaware she's carrying anything, so try to break the news as gently as possible.

If there's no pregnancy or disease, of course, the whole thing is moot.

*This originally said "72 hours," which was the window at one time but no longer is.

Don't just downvote if you disagree with me, write up your own thoughts on the subject also.

anthropod has reminded me that there's a relatively low likelihood of pregnancy from a single act of intercourse. Even a woman who has sex every day for a year has a better than one in nine chance of not getting pregnant that year.