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How Do Birth Control Pills Work to Prevent Unwanted Pregnancy?

How do birth control pills prevent pregnancies? We give you a low-down on the dosage, the potential side effects and more.

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Posted on July 21, 2021 ·

Contraceptive methods are abundant and range all the way from contraceptive implants to condoms, to the highly popular birth control pills. The pill or oral contraception is one of the most used birth control methods around the world. According to the International Institute for Population Science (IIPS), oral contraception (or “the pill”) use rose from 1% in 1992 to 8.6% in 2015 in sexually active women in India and is continuing to rise as access improves across the country.
The most common brands of birth control pills in India are Saheli, Centron, and Unwanted 21 Days, but there are hundreds of more formulations and generic versions of the pill. You can purchase the pill at any pharmacy, but you will need a prescription from your doctor.
Are you wondering how the pill works to prevent pregnancies? Allow us to explain it to you.


What Exactly are Birth Control Pills?

Birth control pills are oral pills comprising of synthetic hormones that help prevent pregnancy. There are two main types of birth control pills: combination pills and progestin-only pills. While the former is made with a progestin and oestrogen, the latter contains only progestin, which makes it safe for breastfeeding mums. You will need to take a pill every day at approximately the same time for it to be fully effective. If you’re worried you may not remember to take it every day, you might want to consider other contraception options instead! (See our article on a full list of options:


How Do They Work?

Combination pillsCombination pills work by preventing the ovaries from releasing eggs, therefore, preventing pregnancy. The progestin in the pill also thickens the cervical mucous, thereby making it difficult for the sperm to enter the uterus and find the egg. Because it contains oestrogen, it contains some extra benefits like making your periods lighter, less crampy, and improving acne. Combination pills are also linked to reducing the risk of ovarian and endometrial cancer. Your doctor can prescribe one of these three types of combination pills.


  1. Monophasic: These pills deliver the same dose of hormones daily and are the most common form of pills. On the last week of the cycle, you can take the seven days of hormone-free pills or placebo pills. During the week of the placebo pills, you can expect to get your period. Usually, these placebo pills contain iron to help prevent anaemia from heavy periods.
  2. Multi-phasic: This formulation is less common, but contains a slightly different dose of oestrogen each week for the first 21 days of your cycle. This is done to mimic the “natural” rise and fall of your menstrual cycle, and can sometimes be helpful for those who are sensitive to oestrogen (e.g. migraines) but are just as effective as monophasic pills. The same iron-containing, hormone-free pills will follow the remaining seven days.
  3. Extended Cycle: If you want to do away with the aunt flow problems every month, then these can be a great option for you. These packs contain 84 active pills and seven days of inactive pills. If you are on these pills, you will only get your period four times a year when you take the inactive pills.

Progestin-only pillsAlso known as the minipill, these prevent the sperm from reaching the eggs by thickening the mucous of the cervix. Unlike combination pills, they do not suppress ovulation consistently. These pills are more likely to be prescribed if you smoke, have chronic nausea, a history of blood clots, are breastfeeding, or can’t take oestrogen for any other health reasons – as determined by your gynaecologist. These are only effective when taken at the same time every day, and if missed, even by 3 hours, require a back-up contraceptive method such as a condom.


Are There Any Potential Side Effects?

Although rare, if you are on the birth control pill, you may experience any of these following side effects.


  • Nausea/ Vomiting
  • Spotting in between periods
  • Breast tenderness
  • Water retention
  • Abdominal cramps
  • Loss of libido
  • Depression
  • Migraines
  • Blood clot (rare)

Talk to your doctor about trying out a different pill if you are struggling with the side effects. There is no one-size-fits-all when it comes to these pills, so you may have to try different pills until you find the right one. That said, wait for three months before picking a new one as it may take a while for your body to adjust to the changes.



How Do You Make the Pills Work Best For You?

Aim to take the pill at the exact time every day or within a one-hour window. Remember that the more irregular you are with your pill timings, the less effective the medicine becomes, especially with progestin-only pills. Need a little remembering to take a pill? Try setting a reminder on your phone or take it when you complete a daily task like brushing your teeth, working out, or just before you go to sleep.

Learn More with Veera Health

If you are a newbie to the birth control pills and have more queries, you can get in touch with one of the gynaecologists on our portal.
Reviewed by: Dr. Shailly Prasad, MD/MBA, Resident Physician, Obstetrics & Gynecology .

Disclaimer: Content on Veera is provided for informational purposes only and is not intended as medical advice or as a substitute for medical advice given by a physician or trained professional.

References:[1] Family Planning Division, Ministry of Health and Family Welfare, Government of India[2] UpToDate


BY Team Veera

Medically Reviewed



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