People who take oral contraceptives, or birth control pills, generally don’t ovulate. During a typical 28-day menstrual cycle, ovulation occurs approximately two weeks before the start of the next period. But cycles can vary widely. In reality, it usually takes place somewhere near the midpoint of your cycle, give or take about four days.

Ovulation is the process in which your ovary releases a mature egg. This is important to track while trying to conceive. During ovulation, the egg can be fertilized by sperm for 12 to 24 hours after it’s released. Sperm can also live inside your body for up to five days.

How does the pill prevent pregnancy?

When taken every day at the same time of day, birth control pills are most effective at regulating your menstrual cycle.

Combination birth control pills contain estrogen and progesterone and help to prevent ovulation. Without ovulation, there’s no egg to be fertilized. The hormones also help thicken cervical mucus, making it harder for sperm to get into your uterus.

The progesterone-only pill, or minipill, helps to prevent pregnancy by:

  • thickening cervical mucus
  • thinning the lining of the uterus
  • suppressing ovulation

However, it doesn’t consistently suppress ovulation as the combination pill does. To be most effective, the minipill should be taken at the same time every day.

Use a backup birth control method for at least the first week of using the pill. Talk with your doctor about what precautions are necessary when starting the pill, to be on the safe side.

Up to 13 out of 100 women on the minipill become pregnant. The minipill isn’t as effective as the combination pill in helping to prevent pregnancy.

With the combination pill, approximately 9 out of 100 women using it will have an accidental pregnancy. When taking the pill, its effectiveness can depend on:

  • whether it’s taken every day around the same time
  • other medications or supplements you might be taking
  • certain medical conditions that interfere with the medication

The pill doesn’t protect against sexually transmitted infections, so it’s still important to use barrier methods like condoms to help reduce your risk for these infections. You should also see a gynecologist regularly for your pelvic exam.

The takeaway

The pill is one method of hormonal birth control that helps to prevent pregnancy. Because of the hormones that alter your menstrual cycle, you don’t ovulate on the combination pill if it’s taken properly. There’s some suppression of ovulation while on the minipill, but it’s not as consistent and it’s still possible or even likely to ovulate on that pill.

The pill might not be right for everyone, especially if you aren’t good at remembering to take medications or if it might be hard for you to commit to taking it every day around the same time. Talk with your doctor about your birth control needs, medications and supplements you’re taking, and whether the pill might be a good contraceptive choice for you.