Oral contraceptives (OCP) is a type of birth control that is designed to be taken orally (Pic. 1). When taken correctly, it works to prevent pregnancy. 

A number of OCP regimens are currently available for provision, including:

  • progestogen only pill - contains the hormone progestogen
  • combined pill (COCPs) - contains both oestrogen and progestogen hormones   

Combination pills usually work by preventing a woman's ovaries from releasing eggs (ovulation). They also thicken the cervical mucus, which keeps sperm from penetrating into the uterus and joining with an egg. The hormones in combination and progestogen-only pills also thin the lining of the uterus. This could prevent pregnancy by interfering with implantation of an embryo.

Depending on the hormone dose throughout the cycle:

  • monophasic - no variation in hormone dose throughout the cycle, typically 21 tablets of estrogen and progestogen, followed by seven tablets of placebo or an iron supplement (Pic. 2)
  • multiphasic - hormone dose varies throughout the cycle

Because OCPs are the most commonly used method and misuse is so common, a significant proportion of unintended pregnancies could be prevented with improved OCP compliance. With perfect use, OCPs have less than 1% risk of failure or unintended pregnancy. However, mistimed pills, poor understanding of instructions, and gaps in use are factors that account for the 9% risk of failure during the first year of use among typical users.

There are risks associated with hormonal birth control, as is the case with most medication. The total amount of years on hormonal birth control might be limiting, if possible, since the risk is very dependent on duration of use. It is known that some cancers need sex hormones to thrive, such as breast cancer, which is why an increased risk of breast cancer has been linked to elevated estrogen levels in women using OCP. Moreover, oral contraceptive use has been shown to increase the risk of cervical cancer and liver cancer. 

Long-term combined OCP use (5 years or more) can potentially affect optimal endometrial growth, leading to a higher cancellation rate and longer stimulation in frozen embryo transfer cycles. Moreover, there is evidence that with long-term use, it may actually make sexual intercourse less enjoyable for many users because decreased sexual desire, sexual arousal and vaginal secretions/lubrication may occur.


The most common side effect is breakthrough bleeding. Vaginal bleeding between periods (spotting) or missed/irregular periods may occur, especially during the first few months of use. Nausea, vomiting, headache, bloating, breast tenderness, swelling of the ankles/feet (fluid retention), or weight change may occur. 

Associated diseases

Antiphospholipid syndrome

Antiphospholipid syndrome (antiphospholipid antibody syndrome), is a state caused by antiphospholipid antibodies. The presence of antiphospholipid antibodies may represent a small but definite additional risk factor for the development of a variety of complications that result from the use of oral contraceptives. It provokes blood clots (thrombosis) in both arteries and veins as well as pregnancy-related complications such as miscarriage, stillbirth, preterm delivery, and severe preeclampsia (onset of high blood pressure and often a significant amount of protein in the urine during pregnancy).

Systemic lupus erythematosus

Systemic lupus erythematosus (SLE), also known simply as lupus, is an autoimmune disease in which the body's immune system mistakenly attacks healthy tissue in many parts of the body. It is known that oral contraceptives may cause a flare of systemic lupus erythematosus (SLE) within several months of beginning treatment, especially with estrogen-containing preparations.

Lupus itself does not cause infertility but some of the drugs used to treat lupus can reduce fertility. However, most lupus patients have normal fertility and can conceive a child within a year of trying to become pregnant.


Breast cancer

Women who used a form of hormonal contraceptives had an increased risk of about twenty percent, compared to the threat of breast cancer for women who used non-hormonal methods. The longer hormonal contraceptives are employed, the greater the risk became.

It’s worth mentioning that there are proven benefits to using oral contraceptives when it comes to other forms of cancer. There’s evidence that it can reduce the risk of ovarian and endometrial cancer, as well as some signs that it can reduce the likelihood of colorectal cancer (bowel cancer and colon cancer). Still, the ideal scenario would be a method that offers these advantages without the elevated risk of breast cancer.

Heart complications

However, an increased risk of breast cancer isn’t the only problem associated with current hormonal birth control. Cardiovascular disease and depression have both been associated with hormonal contraceptives. 

Combined oral contraceptives with more than 50 µg (microgram) of estrogen increase the risk of ischemic stroke and myocardial infarction but lower doses appear safe. 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.

Mood changes

A number of studies have explained some biochemical mechanisms for the effects of oral contraceptive pills on women’s mood changes. In fact they believed that the components of pills such as estrogen and progesterone might cause these behavioral changes. 

A number of investigators believed that rumors and speech about side effects of the pills that generally is said by friends, neighbors and the warning notes on the pill packages would lead to this condition. However, some researchers demonstrated that although oral contraceptive pills could cause mood changes, they believed that it will stabilize after while. Finally, a group of investigators argue that oral contraceptive pills have no effects on mood change at all.

Weight gain

Hormonal contraception is related to change in the metabolism of some nutrients that may lead to an increase in body weight. The risk of obesity was significantly higher after 7 years of hormonal contraception use. 

According to studies, the risk of obesity was neither related to energy intake nor expenditure. The increased risk of obesity in users of hormonal contraception was still significant after controlling for age, parity, initial weight, socioeconomic status, energy intake and expenditure, and parental obesity. We conclude that the risk of obesity is higher in users of hormonal contraception compared to the non-hormonal ones. Users of combination pills face the highest risk of obesity.

Risk factors

The risk of side effects of OCP use could be enhanced by:

  • long term use (>5 years)
  • cigarette smoking
  • alcohol intake
  • family history of certain cancer


In public services, planning, procurement and distribution logistics of those medicines is essential to prevent shortages and ensure access. Spreading information on contraceptive options among prescribers and on sources of access is also essential in a universal system.

Combined oral contraceptive pills were developed to prevent ovulation by suppressing the release of gonadotropins. Combined hormonal contraceptives, including COCPs, inhibit follicular development and prevent ovulation as a primary mechanism of action.

Progestogen negative feedback decreases the pulse frequency of gonadotropin-releasing hormone (GnRH) release by the hypothalamus, which decreases the secretion of follicle-stimulating hormone (FSH) and greatly decreases the secretion of luteinizing hormone (LH) by the anterior pituitary. Decreased levels of FSH inhibit follicular development, preventing an increase in estradiol levels. Progestogen negative feedback and the lack of estrogen positive feedback on LH secretion prevent a mid-cycle LH surge. Inhibition of follicular development and the absence of an LH surge prevent ovulation.

Estrogen was originally included in oral contraceptives for better cycle control (to stabilize the endometrium and thereby reduce the incidence of breakthrough bleeding), but was also found to inhibit follicular development and help prevent ovulation. Estrogen negative feedback on the anterior pituitary greatly decreases the secretion of FSH, which inhibits follicular development and helps prevent ovulation.

Another primary mechanism of action of all progestogen-containing contraceptives is inhibition of sperm penetration through the cervix into the upper genital tract (uterus and fallopian tubes) by decreasing the water content and increasing the viscosity of the cervical mucus.

The estrogen and progestogen in COCPs have other effects on the reproductive system, but these have not been shown to contribute to their contraceptive efficacy:

  • Slowing tubal motility and ova transport, which may interfere with fertilization.
  • Endometrial atrophy and alteration of metalloproteinase content, which may impede sperm motility and viability, or theoretically inhibit implantation.
  • Endometrial edema, which may affect implantation.

Insufficient evidence exists on whether changes in the endometrium could actually prevent implantation. The primary mechanisms of action are so effective that the possibility of fertilization during COCP use is very small. Since pregnancy occurs despite endometrial changes when the primary mechanisms of action fail, endometrial changes are unlikely to play a significant role, if any, in the observed effectiveness of COCPs.

The return of fertility in former OCP users in women who stop use in order to conceive is comparable to that observed with other contraceptive methods. About 20% women achieve a pregnancy in their first cycle after cessation and 80% after 1 year, irrespective of the type of OC used.

It is generally accepted that the health risks of oral contraceptives 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 contraceptive method to no method (pregnancy) is not relevant—instead, the comparison of safety should be among available methods of contraception.

On the other hand, there is a growing number of women who have postponed motherhood and need effective contraception, but without prolonging the return to fertility.


Antiphospholipid syndrome ―sourced from Wikipedia licensed under CC BY-SA 3.0
Systemic lupus erythematosus ―sourced from Wikipedia licensed under CC BY-SA 3.0
Combined oral contraceptive pill ―sourced from Wikipedia licensed under CC BY- SA 3.0
Birth control pill formulations ―sourced from Wikipedia licensed under CC BY-SA 3.0
Cyclic Oral Contraceptive 28 Day Close Up ―by Mg39913201 licensed under CC BY-SA 4.0
Plaquettes de pilule ―by Ceridwen licensed under CC BY-SA 2.0
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