For those who take birth control to make sure pregnancy doesn’t happen, it’s easy to imagine that any failure in taking the medication could result in an often unwanted pregnancy. This is possible, of course, but how can you get pregnant while taking birth control correctly or with minor delays? Is it possible for this to happen?

Let’s start from the main point: how does birth control work in the body1. Birth control pills are small doses of hormones designed to stop the natural progression of a woman’s cycle. Every woman in her reproductive years goes through some hormonal changes over the course of the days.

Initially, progesterone, followed by GnRh, then FSH, and then the start of estrogen. Estrogen in turn stimulates and promotes the growth of follicles, which lead to the development of a dominant follicle — which is, in effect, ovulation itself. Birth control works by preventing this cycle. If you have one constant hormone predominating during the ovulatory cycle, you’ll get consistent hormone levels and, as a consequence, anovulation.

If a woman takes the oral pill correctly and it’s suitable for her body, she has 99.8% protection against pregnancy. So, if you have almost 100% protection, how can you get pregnant while taking birth control?

The issue comes down to two points. The first is the continuity of birth control use. If a woman misses a pill for more than 12 hours, a hormonal gap can be left in her body and this can lead to other hormones becoming active. It’s recommended that you take the missed pill as soon as you remember it.

This situation is even riskier if you miss a pill at the beginning of a pill pack after the usual break before starting the next pack. Ovulation could be triggered after the break because the body is more susceptible due to the previous seven-day medication pause. However, these episodes usually happen when the type of birth control isn’t suitable for that woman’s body, either because the dosage is too low or it contains the wrong hormone.

If vomiting occurs soon after taking the medication (within 30 minutes), it is recommended that the woman take another birth control pill. In cases of diarrhea, medication failures are rarer, as the body almost immediately absorbs the birth control pill in the stomach, rather than in the intestine, but always check with your doctor about what to do in such situations.

The vast majority of birth control pills are based on estrogens or estradiol2. What varies is whether it is purely estradiol or another hormone combined, such as YAZ, which contains 3 mg of drospirenone and 0.02 mg of ethinylestradiol as ethinylestradiol betacyclodextrin clathrate. Quite a mouthful, isn’t it?

That’s why someone who understands their body and these hormones should recommend the best option for you, so you don’t risk taking a dosage that’s too low or the wrong type of birth control. Sometimes, the best for you is a birth control based on progesterone or a combination of both. The wrong type of contraceptive can indeed result in pregnancy, and in most cases, that’s not the woman’s intention. She really just wants to be protected against an unwanted pregnancy.

How to Get Pregnant While Taking Injectable Birth Control

Frequent breakthrough bleeding may indicate the injection is not working as it should. The injectable birth control is the one that can cause more problems3. Some women do not react well to it and have recurrent breakthrough bleeding. Just as with injectable birth control, breakthrough bleeding may indicate that something is wrong. Maybe it’s not the right type of birth control for your body.

So, if you have frequent breakthrough bleeding, a fertile window can occur in your cycle and you may become pregnant. These cases are more common with injectable medication, just as pregnancy can happen if you miss a birth control pill for one or two days.

Taking the injectable on the wrong day can also make ovulation more likely. The timing for restarting contraception varies by medication, but for most, the first dose is given on the first day of menstruation and, in the following months, on the 8th day of the menstrual cycle, even if there is no more bleeding or flow.

Some medications consider it safe to take the shot up to the 10th day of the cycle, but effectiveness drops by 50% and pregnancy can then occur. Pay attention with the injections taken every 3 months; these are progesterone based and can make breakthrough bleeding and pregnancy more likely. The key in these cases is to check if your body responds better to progesterone than estrogens, and always follow the advice of your gynecologist who will consider your particular situation.

I was once asked if it’s possible to get pregnant by taking birth control continuously. That’s an isolated case, similar to medications that cause breakthrough bleeding, but it’s still not a situation with 100% certainty. Contraception is effective if your body adapts well to the medication. If that’s the case, you have a 99.9% protection rate as well.

I should remind you that taking antibiotics can neutralize the effect of any hormonal contraceptive and make ovulation easier. So, if you’ve had to take any antibiotics, it’s best to use a condom and avoid withdrawal at all costs, because that can result in pregnancy even if there is no internal ejaculation.

How to get pregnant while taking birth control can also be a question for those who feel like giving in to nature’s call. Failures can happen, but you are much more likely to get pregnant if you stop taking the medication. To do so, talk to your doctor to do it the right way and without surprises. See also: Continuous Birth Control and Its Benefits