Thanks for your question.To start a sexual relationship and to reduce the chances of STIs it is good to use precautions.Today in the market there are number of contraception are there and they have different ways to use them and different contraception suit different people.Going through these contraception have some advantages and have some disadvantages because everybody has different genital structure. While using the contraception it is good if you follow their instruction as it is a best way which reduces the risk of pregnancy but there is no contraception which is fully or 100% effictive. It means that there will be a chance or a risk may be their, butthe risk of STIs (sexually transmitted infection) and pregnancy is less by using the contraception or precautions. Today people use condoms because it is safer and good and if we use condoms according to their instruction then it is really 98% effective in reducing pregnancy and STIs,as well as they also use contraceptive pill which is 99% effective in reducing STIs and pregnancy if use according to the instruction as given.This is one of the good way for the protection called dual protection method. If your mind is still worried about your girlfriend getting pregnant then it is good to have a talk to any doctor or any nurse in person,because a doctor or a nurse in person can give you a better advise and can make you explain in a more broader way .Even you along with your girlfriend can go to any doctor or any family planning clinic for you consult.You will get the advice which will be best for you and contraception is free.Consulting a doctor in person can make you better understand the process of using contracepton .Take care