What Are Hormonal Methods of Contraception?

Hormonal birth control, often in the form of a daily pill, alters the delicate balance of hormones in a woman's body to prevent ovulation.

Contraception refers to the precautions taken before and/or after vaginal intercourse to prevent pregnancy. The hormonal method of contraception involves the use of hormones by the woman on a regular basis, and is one of the most effective methods of contraception.

Contraceptive hormones are available in the form of

• Pills
• Injections
• Implants under the skin
• Vaginal rings
• Skin patches

Certain intrauterine devices also come with a hormone delivery system. Currently hormonal contraceptives are available only for women, but efforts are on to develop male hormonal contraceptive that can inhibit sperm production.

The woman’s body produces and maintains a fine balance of different sex hormones that aid ovulation and pregnancy. Hormonal contraception works at different levels to prevent pregnancy by disrupting the normal hormonal balance.

Hormonal contraceptives are formulations of progestin or a combination of progestin and estrogen. Hormonal contraception results from a combination of the following:

• Suppression of ovulation
• Thickening of cervical mucus that hinders the passage of sperm
• Thinning of the uterus lining (endometrium) which prevents implantation of the fertilized egg

People who smoke or are over the age of 35 should avoid using hormonal birth control. Other conditions that preclude hormonal contraception include:

• Coronary artery disease
• Cerebrovascular disease
• Deep vein thrombosis and/or pulmonary embolism
• High blood pressure
• Congestive heart failure
• Vascular complications from diabetes
• Estrogen-dependent tumors or breast cancer
• Abnormal vaginal bleeding
• Known or suspected pregnancy
• Liver, kidney or adrenal gland problems

Oral contraceptives

Oral contraceptives are hormonal pills for women. Dosage is one pill a day at the same time every day, starting on the first day of the period or the first Sunday after the period starts. Oral contraceptives are of two primary types:

Progestin-only oral contraceptive (mini-pills)

Mini-pills do not contain estrogen and are not widely used in the United States. Progestin-only pills are suitable for women who are breastfeeding or cannot take estrogen for any reason.

• Efficacy: Failure rate with typical use is 7% in the first year of use.
• Advantages:
  • Without estrogen, risk of blood clots (thromboembolism) is minimal.
  • Decreases menstrual cramps, blood loss and premenstrual symptoms.
• Disadvantages:
  • If a pill is missed, a backup contraception is required.
  • Unscheduled bleeding and spotting may occur.
  • Side effects such as
  • Nausea
  • Breast tenderness
  • Headache
  • Amenorrhea (lack of menstruation)

Combination oral contraceptives

Combination oral contraceptives contain progestin and ethinyl estradiol, a form of estrogen. Several formulations of combination contraceptives are available which come in packs of:

• 21-day pills: taken in 21-day cycles with seven no-pill days during which period menstruation should occur.
• 28-day pills: taken in 28-day cycles with hormonally active pills for 21 days and placebos for seven days. Having no gap in ingestion makes compliance easier.
• 91-day pills: taken in 91-day cycles with combination pills for 84 days and estrogen-only or placebo pills for seven days. Menstruation occurs only once in three months.
• 365-day pills: low-dose combination pills taken every day for a whole year. Periods may get lighter or stop altogether.

Current available formulations have lower dosages of estrogen than when hormonal birth control first entered the market. This made oral contraception safer and reduced the side effects. 

• Efficacy: Failure rate ranges from 0.1% with perfect use to 5% for typical use.
• Advantages:
  • Regular menstruation
  • Reduced bleeding helps increase iron levels in anemic women
  • Women can manipulate their cycles by changing the regimen
  • Prevents ectopic pregnancies and ovarian cysts
  • Prevents pelvic inflammatory disease
  • Protection for up to 15 years after discontinuation, against certain malignant cancers such as
  • Epithelial ovarian cancer (40% reduced risk)
  • Endometrial adenocarcinoma (50% reduced risk)
• Disadvantages:
  • No protection from sexually transmitted diseases
  • Side effects such as
  • Nausea
  • Breast tenderness
  • Breakthrough bleeding
  • Headache
  • Amenorrhea
  • Delay in ovulation cycles after discontinuation
  • Interactions with certain drugs such as rifampin

Emergency postcoital oral contraceptives

Emergency oral contraceptives can be taken within 120 hours (optimum efficacy up to 72 hours) after unprotected vaginal intercourse or after a suspected/known contraceptive failure. Emergency pills prevent pregnancy primarily by delaying ovulation.

• Efficacy: Efficacy depends on the unprotected intercourse and ovulation timings.
• Advantages: Prevents half to two-thirds of pregnancies if taken within 72 hours.
• Disadvantages:
  • Not effective if fertilization and implantation has taken place.
  • Side effects such as
  • Nausea and vomiting
  • Breast tenderness
  • Headache
  • Dizziness
  • Fatigue
  • Abdominal pain

Metabolic effects of oral contraceptives

With the development of low-dose estrogen pills, safety has greatly improved. Risks from combination oral contraceptives include

• Venous thrombosis: Estrogen activates blood clotting and is a high risk for women who
  • Smoke heavily
  • Are obese or have abnormal blood fat levels
  • Have severe diabetes with artery damage
  • Have high blood pressure
• Hypertension: Estrogen elevates blood pressure and is not recommended for women with hypertension.
• Atherogenesis and stroke: Some of the androgen and progestin hormones may increase low-density lipoproteins (LDL) levels in blood, hence unsuitable for women at risk for cardiovascular disease.
• Hepatocellular adenoma: Benign liver tumors associated with oral contraceptives, which pose a risk of rupture of the liver’s covering (capsule). These may lead to extensive bleeding or even death.
• Breast and cervical cancer: The risk of breast or cervical cancer from oral contraceptive use is controversial. Studies indicate that the increase in risk for breast cancer is minimal or none. Risk for cervical cancer is minimal, although an annual Pap smear test is recommended. 
  • Risk factors for cervical cancer are early sexual intercourse and human papillomavirus (HPV) exposure.

Contraceptive injections

A progestin-only formulation known as depomedroxyprogesterone acetate (DMPA) given as an intramuscular injection is effective for three months. A subcutaneous version with a lower dose of medroxyprogesterone acetate (MPA) is available now, but efficacy requires further study.

• Efficacy: DMPA is extremely effective and the failure rate is 0.3% in the first year of perfect use.
• Advantages:
  • Safe for women who cannot take estrogen or are breastfeeding
  • Has less risk of thromboembolism
  • Reduced bleeding and menstrual cramps
  • Reduced risk of endometrial and ovarian cancer
• Disadvantages:
  • Requirement of clinic visit for intramuscular injection every three months.
  • Irregular bleeding and amenorrhea in 50% of women within the first year
  • Delayed return to fertility with long-term use
  • Delayed withdrawal of side effects such as
  • Weight gain
  • Depression
  • Menstrual irregularities
  • Bone density loss

Subcutaneous contraceptive implants

A subcutaneous implant consists of a thin, 4-cm rod implanted usually under the skin in the triceps area in the upper arm of the woman. The rod contains progestin (desogestrel or etonogestrel), which is released in a prescribed dosage every day.

• Efficacy: A contraceptive implant is more effective than surgical sterilization. With proper insertion the failure rate is 0.05% for at least three years.
• Advantages:
  • Longevity of the implant
  • Lack of estrogen-based risks such as thromboembolism
  • Immediate return to fertility upon removal
  • No adverse effect on breast milk production
• Disadvantages:
  • A minor surgical procedure is required for implant and removal. Biodegradable implants are in clinical trials.
  • Side effects such as
  • Menstrual irregularities
  • Breast tenderness
  • Headaches
  • Moodiness

Combination skin patch contraceptives

Skin patch contraceptives are applied on the skin and contain a combination of an estrogen (ethinyl estradiol) and a progestin (levonorgestrel or norelgestromin). The patch releases hormones in prescribed dosage for a week, and three patches are used for three consecutive weeks with a week’s gap before the next cycle.

• Efficacy: Failure rate is one pregnancy per 100 women in one year, similar to other combination methods.
• Advantages:
  • Easier compliance
  • Reduced side effects such as nausea and vomiting as it is not metabolized by the liver
• Disadvantages:
  • May cause skin irritation
  • May get dislodged unnoticed
  • Risk for thromboembolism
  • Less effective for women with body mass index (BMI) higher than 30 

Contraceptive vaginal ring

A flexible ring containing etonogestrel/ethinyl estradiol (NuvaRing) combination is placed inside the vagina. The ring releases a prescribed dosage of hormones, daily for three weeks. The reproductive organs directly absorb the hormones.

The contraceptive vaginal ring is placed within five days from the start of menstruation. After three weeks of wearing the ring, the woman removes it for a week, and then replaces it with a new ring. A reusable ring (Annovera) with a combination of segesterone/ethinyl estradiol can be used for a year.

• Efficacy: With NuvaRing less than one in 100 women become pregnant in a year of perfect use. Clinical trials with Annovera show two to four in 100 women get pregnant in one year.
• Advantages:
  • Ease of use and rapid return to fertility upon discontinuation
  • Reduced side effects such as nausea and vomiting because of low estrogen dose
  • Not metabolized by the liver
• Disadvantages:
  • Side effects such as
  • Headaches
  • vaginal discharge
  • irritation
  • The ring may slip out accidentally
  • Either partner may feel the ring during intercourse