Editing Combined oral contraceptive pill (section)

===Hypercoagulability===

Estrogen in high doses can increase risk of blood clots. All combined oral contraceptive pill users have a small increase in the risk of venous thromboembolism compared with non-users; this risk is greatest within the first year of combined oral contraceptive pill use.<ref name=":6">{{cite journal | vauthors = Black A, Guilbert E, Costescu D, Dunn S, Fisher W, Kives S, Mirosh M, Norman WV, Pymar H, Reid R, Roy G, Varto H, Waddington A, Wagner MS, Whelan AM | title = No. 329-Canadian Contraception Consensus Part 4 of 4 Chapter 9: Combined Hormonal Contraception | journal = Journal of Obstetrics and Gynaecology Canada | volume = 39 | issue = 4 | pages = 229–268.e5 | date = April 2017 | pmid = 28413042 | doi = 10.1016/j.jogc.2016.10.005 }}</ref> Individuals with any pre-existing medical condition that also increases their risk for blood clots have a more significant increase in risk of thrombotic events with combined oral contraceptive pill use.<ref name=":6" /> These conditions include but are not limited to high blood pressure, pre-existing [[cardiovascular disease]] (such as [[valvular heart disease]] or [[Coronary artery disease|ischemic heart disease]]<ref name=":4">{{cite book|vauthors=Cooper DB, Patel P, Mahdy H|chapter=Oral Contraceptive Pills|date=2019|chapter-url=http://www.ncbi.nlm.nih.gov/books/NBK430882/|title=StatPearls|publisher=StatPearls Publishing|pmid=28613632|access-date=5 August 2019|archive-date=3 May 2019|archive-url=https://web.archive.org/web/20190503071035/https://www.ncbi.nlm.nih.gov/books/NBK430882/|url-status=live}}</ref>), history of thromboembolism or pulmonary embolism, cerebrovascular accident, and a familial tendency to form blood clots (such as familial [[factor V Leiden]]).<ref name="webmdbcp2">{{cite web|url=http://www.webmd.com/sex/birth-control/birth-control-pills?page=5#1|title=Can Any Woman Take Birth Control Pills?|website=WebMD|access-date=8 May 2016|archive-date=3 May 2016|archive-url=https://web.archive.org/web/20160503120843/http://www.webmd.com/sex/birth-control/birth-control-pills?page=5#1|url-status=live}}</ref> There are conditions that, when associated with combined oral contraceptive pill use, increase risk of adverse effects other than thrombosis. For example, women with a history of [[migraine]] with aura have an increased risk of [[stroke]] when using combined oral contraceptive pills, and women who [[Tobacco smoking|smoke]] over age 35 and use combined oral contraceptive pills are at higher risk of [[myocardial infarction]].<ref name="who mec" />