Editing Combined oral contraceptive pill (section)

===Role of placebo pills===
The role of the [[placebo]] pills is two-fold: to allow the user to continue the routine of taking a pill every day and to simulate the average [[menstrual cycle]]. By continuing to take a pill every day, users remain in the daily habit even during the week without hormones. Failure to take pills during the placebo week does not impact the effectiveness of the pill, provided that daily ingestion of active pills is resumed at the end of the week.{{citation needed|date=July 2023}}

The placebo, or hormone-free, week in the 28-day pill package simulates an average menstrual cycle, though the hormonal events during a pill cycle are significantly different from those of a normal ovulatory menstrual cycle. Because the pill suppresses ovulation (to be discussed more in the [[#Mechanism of action|Mechanism of action section]]), birth control users do not have true menstrual periods. Instead, it is the lack of hormones for a week that causes a withdrawal bleed.<ref name=":13"/> The withdrawal bleeding that occurs during the break from active pills has been thought to be reassuring, a physical confirmation of not being pregnant.<ref name="gladwell2">{{cite magazine| vauthors = Gladwell M |date=10 March 2000|title=John Rock's Error|url=http://www.gladwell.com/2000/2000_03_10_a_rock.htm|magazine=The New Yorker|archive-url=https://web.archive.org/web/20130511133811/http://www.gladwell.com/2000/2000_03_10_a_rock.htm|archive-date=11 May 2013|access-date=4 February 2009}}</ref> The withdrawal bleeding is also predictable. Unexpected breakthrough bleeding can be a possible side effect of longer term active regimens.<ref>{{cite web|url=http://www.mayoclinic.com/health/birth-control-pill/WO00098|title=Birth control pill FAQ: Benefits, risks and choices|last=Mayo Clinic staff|publisher=Mayo Clinic|access-date=1 February 2013|archive-date=26 December 2012|archive-url=https://web.archive.org/web/20121226060838/http://www.mayoclinic.com/health/birth-control-pill/WO00098|url-status=live}}</ref>

Since it is not uncommon for menstruating women to become anemic, some placebo pills may contain an [[iron]] supplement.<ref>{{cite web|url=http://www.patentstorm.us/patents/6451778/description.html|title=US Patent:Oral contraceptive:Patent 6451778 Issued on September 17, 2002 Estimated Expiration Date: July 2, 2017.|publisher=PatentStorm LLC|archive-url=https://web.archive.org/web/20110613020809/http://www.patentstorm.us/patents/6451778/description.html|archive-date=13 June 2011|url-status=dead|access-date=19 November 2010}}</ref><ref name="pmid11683548">{{cite journal | vauthors = Hercberg S, Preziosi P, Galan P | title = Iron deficiency in Europe | journal = Public Health Nutrition | volume = 4 | issue = 2B | pages = 537–545 | date = April 2001 | pmid = 11683548 | doi = 10.1079/phn2001139 | doi-access = free | title-link = doi }}</ref> This replenishes iron stores that may become depleted during menstruation. As well, birth control pills, such as combined oral contraceptive pills, are sometimes fortified with [[Folate|folic acid]] as it is recommended to take folic acid supplementation in the months prior to pregnancy to decrease the likelihood of [[neural tube defect]] in infants.<ref>{{cite journal | vauthors = Viswanathan M, Treiman KA, Kish-Doto J, Middleton JC, Coker-Schwimmer EJ, Nicholson WK | title = Folic Acid Supplementation for the Prevention of Neural Tube Defects: An Updated Evidence Report and Systematic Review for the US Preventive Services Task Force | journal = JAMA | volume = 317 | issue = 2 | pages = 190–203 | date = January 2017 | pmid = 28097361 | doi = 10.1001/jama.2016.19193 }}</ref><ref>{{cite journal | vauthors = Lassi ZS, Bhutta ZA | title = Clinical utility of folate-containing oral contraceptives | journal = International Journal of Women's Health | volume = 4 | pages = 185–190 | date = April 2012 | pmid = 22570577 | pmc = 3346209 | doi = 10.2147/IJWH.S18611 | doi-access = free | title-link = doi }}</ref>