It is generally accepted that the health risks of oral<unk> s are lower than those from pregnancy and birth, and "the health benefits of any method of contraception are far greater than any risks from the method". Some organizations have argued that comparing a<unk>  method to no method (pregnancy) is not relevant—instead, the comparison of safety should be among available methods of contraception. Common Different sources note different incidences of side effects. The most common side effect is breakthrough bleeding. A 1992 French review article said that as many as 50% of new first-time users discontinue the birth control pill before the end of the first year because of the annoyance of side effects such as breakthrough bleeding and amenorrhea. A 2001 study by the Kinsey Institute exploring predictors of discontinuation of oral<unk> s found that 47% of 79 women discontinued the pill. One 1994 study found that women using birth control pills blinked 32% more often than those not using the contraception. On the other hand, the pills can sometimes improve conditions such as dysmenorrhea, premenstrual syndrome, and acne, reduce symptoms of endometriosis and polycystic ovary syndrome, and decrease the risk of anemia. Use of oral<unk> s also reduces lifetime risk of ovarian and endometrial cancer. Nausea, vomiting, headache, bloating, breast tenderness, swelling of the ankles/feet (fluid retention), or weight change may occur. Vaginal bleeding between periods (spotting) or missed/irregular periods may occur, especially during the first few months of use. Heart and blood vessels Combined oral<unk> s increase the risk of venous thromboembolism (including deep vein thrombosis (DVT) and pulmonary embolism (PE)). While lower doses of estrogen in COC pills may have a lower risk of stroke and myocardial infarction compared to higher estrogen dose pills (50 μg/day), users of low estrogen dose COC pills still have an increased risk compared to non-users. These risks are greatest in women with additional risk factors, such as smoking (which increases risk substantially) and long-continued use of the pill, especially in women over 35 years of age. The overall absolute risk of venous thrombosis per 100,000 woman-years in current use of combined oral<unk> s is approximately 60, compared with 30 in non-users. The risk of thromboembolism varies with different types of birth control pills; compared with combined oral<unk> s containing levonorgestrel (LNG), and with the same dose of estrogen and duration of use, the rate ratio of deep venous thrombosis for combined oral<unk> s with norethisterone is 0.98, with norgestimate 1.19, with desogestrel (DSG) 1.82, with gestodene 1.86, with drospirenone (DRSP) 1.64, and with cyproterone acetate 1.88. In comparison, venous thromboembolism occurs in 100–200 per 100.000 pregnant women every year. One study showed more than a 600% increased risk of blood clots for women taking<unk> s with drospirenone compared with non-users, compared with 360% higher for women taking birth control pills containing levonorgestrel. The U.S. Food and Drug Administration (FDA) initiated studies evaluating the health of more than 800,000 women taking<unk> s and found that the risk of VTE was 93% higher for women who had been taking drospirenone<unk> s for 3 months or less and 290% higher for women taking drospirenone<unk> s for 7–12 months, compared with women taking other types of oral<unk> s. Based on these studies, in 2012 the FDA updated the label for drospirenone<unk> s to include a warning that<unk> s with drospirenone may have a higher risk of dangerous blood clots. Cancer A systematic review in 2010 did not support an increased overall cancer risk in users of<unk> s, but did find a slight increase in breast cancer risk among current users, which disappears 5–10 years after use has stopped. Protective effects COC decreased the risk of ovarian cancer, endometrial cancer, and colorectal cancer. Two large cohort studies published in 2010 both found a significant reduction in adjusted relative risk of ovarian and endometrial cancer mortality in ever-users of OCs compared with never-users. The use of oral<unk> s (birth control pills) for five years or more decreases the risk of ovarian cancer in later life by 50%. Combined oral<unk>  use reduces the risk of ovarian cancer by 40% and the risk of endometrial cancer by 50% compared with never users. The risk reduction increases with duration of use, with an 80% reduction in risk for both ovarian and endometrial cancer with use for more than 10 years. The risk reduction for both ovarian and endometrial cancer persists for at least 20 years. Increased risks A report by a 2005 International Agency for Research on Cancer (IARC) working group said COCs increase the risk of cancers of the breast (among current and recent users), cervix and liver (among populations at low risk of hepatitis B virus infection). A 2013 meta-analysis concluded that every use of birth control pills is associated with a modest increase in the risk of breast cancer (relative risk 1.08) and a reduced risk of colorectal cancer (relative risk 0.86) and endometrial cancer (relative risk 0.57). Cervical cancer risk in those infected with human papilloma virus is increased. A similar small increase in breast cancer risk was seen in other meta analyses. Weight A 2013 Cochrane systematic review found that studies of combination hormonal<unk> s showed no large difference in weight when compared with placebo or no intervention groups. The evidence was not strong enough to be certain that<unk>  methods do not cause some weight change, but no major effect was found. This review also found "that women did not stop using the pill or patch because of weight change." Sexuality<unk> s may increase natural vaginal lubrication. Other women experience reductions in libido while on the pill, or decreased lubrication. Some researchers question a causal link between<unk>  use and decreased libido; a 2007 study of 1700 women found<unk>  users experienced no change in sexual satisfaction. A 2005 laboratory study of genital arousal tested fourteen women before and after they began taking<unk> s. The study found that women experienced a significantly wider range of arousal responses after beginning pill use; decreases and increases in measures of arousal were equally common. A 2006 study of 124 pre-menopausal women measured sex hormone binding globulin (SHBG), including before and after discontinuation of the oral<unk>  pill. Women continuing use of oral<unk> s had SHBG levels four times higher than those who never used it, and levels remained elevated even in the group that had discontinued its use. Description of the study results in Medical News Today: Theoretically, an increase in SHBG may be a physiologic response to increased hormone levels, but may decrease the free levels of other hormones, such as androgens, because of the unspecificity of its sex hormone binding. A 2007 study found the pill can have a negative effect on sexual attractiveness: scientists found that lapdancers who were in estrus received much more in tips than those who weren't, while those on the oral<unk>  pill had no such earnings peak. Depression Low levels of serotonin, a neurotransmitter in the brain, have been linked to depression. High levels of estrogen, as in first-generation<unk> s, and progestin, as in some progestin-only<unk> s, have been shown to lower the brain serotonin levels by increasing the concentration of a brain enzyme that reduces serotonin. A growing body of research evidence has suggested that hormonal contraception may have an adverse effect on women's psychological health. In 2016, a large Danish study of one million women (followed-up from January 2000 to December 2013) showed that use of<unk> s, especially among adolescents, was associated with a statistically significantly increased risk of subsequent depression, although the sizes of the effects are small (for example, 2.1% of the women who took any form of oral birth control were prescribed anti-depressants for the first time, compared to 1.7% of women in the control group). Similarly, in 2018, the findings from a large nationwide Swedish cohort study investigating the effect of hormonal contraception on mental health amongst women (n=815,662, aged 12–30) were published, highlighting an association between hormonal contraception and subsequent use of psychotropic drugs for women of reproductive age. This association was particularly large for young adolescents (aged 12–19). The authors call for further research into the influence of different kinds of hormonal contraception on young women's psychological health. Progestin-only<unk> s are known to worsen the condition of women who are already depressed. However, current medical reference textbooks on contraception and major organizations such as the American ACOG, the WHO, and the United Kingdom's RCOG agree that current evidence indicates low-dose combined oral<unk> s are unlikely to increase the risk of depression, and unlikely to worsen the condition in women that are currently depressed. Hypertension Bradykinin lowers blood pressure by causing blood vessel dilation. Certain enzymes are capable of breaking down bradykinin (Angiotensin Converting Enzyme, Aminopeptidase P). Progesterone can increase the levels of Aminopeptidase P (AP-P), thereby increasing the breakdown of bradykinin, which increases the risk of developing hypertension. Other effects Other side effects associated with low-dose<unk> s are leukorrhea (increased vaginal secretions), reductions in menstrual
Combined oral contraceptive pill
Oral contraceptive pill
Male contraceptive
Extended cycle combined hormonal contraceptive
Estradiol-containing birth control pill
Heat-based contraception
Female condom
Combined hormonal contraception