Medicine 2: Combined Oral Contraceptives

Medicine 2: Combined Oral Contraceptives

What is it?

Combination birth control pills, also known as the pill, are oral contraceptives that contain estrogen and a progestin.

Combination birth control pills come in different mixtures of active and inactive pills, including:

Conventional pack: One common type contains 21 active pills and seven inactive pills. Inactive pills do not contain hormones. Formulations containing 24 active pills and four inactive pills, known as a shortened pill-free interval, also are available. Some newer pills may contain only two inactive pills. You take a pill every day and start a new pack when you finish the old one. Packs usually contain 28 days of pills. Bleeding may occur every month during the time when you take the inactive pills that are at the end of each pack.

Extended-cycle pack: These packs typically contain 84 active pills and seven inactive pills. Bleeding generally occurs only four times a year during the seven days you take the inactive pills.

Continuous-dosing pack: A 365-day pill also is available. You take this pill every day at the same time. For some people, periods stop altogether. For others, periods become significantly lighter. You do not take any inactive pills¹.

How does it work?

Combination pills contain synthetic versions of estrogen and progesterone, and they work by stopping ovulation.

At first, it gives a steady dose of estrogen with no peak so there is no signal to ovaries to release an egg. Then the pill starts delivering a fixed level of progesterone throughout its use to stop the uterine lining from growing.

Finally, most pills have a week of placebos, which make hormone levels fall and your period starts. It’s actually called withdrawal bleeding when you’re on the pill because it’s a reaction to the loss of hormones.

Because the pill delivers everything in steady doses, it can make your hormone levels more predictable and your period symptoms less unpleasant¹.

What is the efficacy?

A random effect Bayesian pairwise and network meta-analysis was conducted with change in premenstrual depressive symptoms and overall premenstrual symptomatology between baseline and 3 cycles as outcome.

Results: Of 3664 records, 9 eligible trials were included that studied 1205 women with premenstrual syndrome or premenstrual dysphoric disorder (mean age per study range, 24.6-36.5 years). The pairwise meta-analysis revealed that combined oral contraceptives were more efficacious than placebo in treating overall premenstrual symptomatology, but not premenstrual depressive symptoms specifically. However, none of the combined oral contraceptives were more effective than each other in reducing premenstrual depressive symptoms and overall premenstrual symptomatology.

Conclusion: Combined oral contraceptives may improve overall premenstrual symptomatology in women with premenstrual syndrome or premenstrual dysphoric disorder, but not premenstrual depressive symptoms. There is no evidence for one combined oral contraceptive being more efficacious than any other².

Side effects:

Short-term effects: Nausea, headache, irritability and moodiness, breast tenderness¹.

Long-term effects: Long-term side effects of birth control pills may include a higher risk of blood clots and some cancers. However, hormonal methods of birth control are safe for most people, as long as they have a doctor’s approval³.

References

1. Cooper DB, Patel P. Oral contraceptive pills [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan–. [cited 2025 Apr 23]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK430882/
2. de Wit AE, de Vries YA, de Boer MK, Scheper C, Fokkema A, Janssen CAH, Giltay EJ, Schoevers RA. Efficacy of combined oral contraceptives for depressive symptoms and overall symptomatology in premenstrual syndrome: pairwise and network meta-analysis of randomized trials. Am J Obstet Gynecol. 2021 Dec;225(6):e1–e13. doi: 10.1016/j.ajog.2021.06.090.

3. Smith JS, Green J, Berrington de Gonzalez A, Appleby P, Peto J, Plummer M, Franceschi S, Beral V. Cervical cancer and use of hormonal contraceptives: a systematic review. Lancet. 2003 Apr 5;361(9364):1159–67. doi: 10.1016/s0140-6736(03)12949-2.