The oral contraceptive pill is one of the most effective forms of female birth control. When taken properly it is over 99% effective at preventing pregnancy. However, this level of efficacy only comes if you take your pill at the exact same time every single day. We’re only human and sometimes might forget to take a pill, or don’t always take it at the exact same time. That’s why with more typical usage, the effectiveness rate of the birth control pill lowers to closer to 92%.
While 92% is still quite high, this means that about 8 out of 100 oral contraceptive users may get pregnant each year.
How do birth control pills work?
There are two types of birth control pills: the combined pill and the mini pill. The combined pill contains a combination of estrogen and progestin while the mini pill contains progestin only. Both pills are equally effective at preventing pregnancy when taken correctly - ie: at the exact same time every day. By doing so, you’re regulating the amount of hormones that are in your body at any given time.
If you’re taking the combined pill, the estrogen and progestin work together to stop ovulation from occuring. This means that during each monthly cycle, there is no egg to be fertilised. It also thickens the cervical mucus which makes it harder for sperm to enter the womb, and thins the uterine lining to make it difficult for fertilised eggs to implant.
If you’re taking the mini pill, the progestin thickens the mucus around the cervix while simultaneously thinning the lining of your uterus. In some women, the mini pill stops ovulation from happening in the first place like the combined pill.
In order for these hormones to do their job and help prevent pregnancy, there needs to be a certain level in your body at any given time. That’s why both the combined pill and the mini pill are prescribed to be taken at the exact same time every day - to maintain the levels of hormones in your body.
3 ways you can get pregnant on the pill
Now that we understand how the contraceptive pill works to stop pregnancy, let’s dive into 3 ways that you can get pregnant on the pill.
1. Missing a pill or not taking it at the same time each day
If you don’t take it at the same time, or miss a pill, this can cause a decrease in the hormones in your body. This means that you can get pregnant while on the pill.
You do have a bit of wiggle room though - if you’re on the combined pill, a pill is not considered missed until it is more than 24 hours late, or 48 hours from when you took the last one. If you miss a pill, take it as soon as possible even if that means you have to take two in the same day. If you missed two or more in a pack, take the last one you missed as soon as possible and then continue on with the pack as usual. Use condoms for 7 days as backup protection.
If you’re on the mini pill, you only have a 3 hour window to take your missed pill. If it’s been longer than that, still take the missed pill as soon as you can, but make sure you use backup contraception for at least 3 days.
2. Vomiting or diarrhea
Vomiting or having diarrhea can cause your body to not absorb the pill. You may even throw up the pill. If you vomit shortly after taking your pill, you should take another one as soon as you can to replace the one you’ve thrown up. If you have diarrhea for more than 2 days, this can also lower the effectiveness rate of the pill.
3. Taking certain medications
Some medications are known to interfere with oral contraceptives. These include:
- Antibiotics like Rifampin
- Some HIV medicines
- Anti epilepsy drugs
- Supplements like St Johns wort
Always tell your doctor what medications you’re taking so they can best advise you on how to approach your treatment plan.
While the pill is one of the most popular and most effective forms of hormonal birth control for women, it’s not foolproof. It is possible to get pregnant while taking the pill, generally due to human error. However, we have some leeway with how much time we have before a pill is considered missed. If you’re on the combined pill, you have 24 hours. With the mini pill, you have 3 hours. If in doubt, use backup contraception like condoms until you feel confident that you’re back on track.
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