There is no form of birth control that is actually 100% effective because even when you have a procedure like a permanent sterilization, there is still a risk of pregnancy because you still have a uterus and you still have sperm that can actually fertilize an egg. Although this is very rare, as most sterilizations are 99% effective - this is why we never say 100%.
Birth control is a form of contraception. They come in many forms and types and they are used to help prevent pregnancy. However, we also use it sometimes to help with menstrual regulation.
Most birth control is actually about 98% effective, but the problem is that people are not compliant. That is: if you don't take your birth control pill every day, you have a higher risk of getting pregnant. If you don't put your patch on every week, you have a higher risk of getting pregnant. If you don't put the NuvaRing in every 3 weeks (or 3 weeks in and 1 week off) - you have a higher risk of getting pregnant. If you don't come in and get your shot every 3 months, you have a higher risk of getting pregnant. As you can see, we have a continuous pattern here. It's when you don't do what you're supposed to do in taking whatever form of contraception you've chosen is right for you, is oftentimes the most common reason of why people conceive on contraception.
If you're stopping your birth control in efforts to conceive (that is get pregnant) then it's often advisable to start prenatal vitamins prior to even the cessation or stopping of the birth control that you're using. It's recommended to start your pregnancy prenatal vitamins approximately 1-2 months prior to you actually stopping your birth control. The reasoning behind this is that if you get pregnant in a soon or quick interval of cessation, then you will actually have the protective component of primarily folic acid and/or DHA. Folic acid actually helps the neuro tube which is developed in the first 4-6 weeks of life, and oftentimes women do not even realize they are pregnant until after this time.
There are various types of birth control. There are the barrier methods which include the condom, the cervical cup, the sponge, and the diaphragm. Then there are some hormonal components like the birth control pill, the patch, the ring, and the shot. Then there's also what we call LARCs, which are Long Acting Reversible Contraceptions. That includes the implant in the arm or Nexplanon, and then there's also IUDs (or intrauterine devices) which are several types.
When a person is deciding what birth control works for them, they first and foremost have to be honest with themselves about what type of person they are. Some people can do something every day, others would be noncompliant and forget, and so you have to realize what's going to fit your lifestyle.