Contraception for women: an evidence based overview

The family planning consultation

How do hormonal contraceptives work?

How effective are hormonal contraceptives?

Effectiveness is related to the acceptability of the contraceptive method and to compliance. “Typical use” is considerably less effective than “perfect use” (correct and consistent use). A recent Cochrane review found that combined oral contraceptive pills, transdermal patches, and vaginal rings were equally efficacious7: they have a failure rate of 0.3 per 100 women per year with perfect use and 8 with typical use.7 8 Maintaining a regular schedule is more important for progestogen-only pills than for combined oral contraceptives—more than a three hour delay in taking the progestogen-only pill can cause failure of contraception. Implants, injectable preparations, and intrauterine contraceptives do not depend on daily compliance and have lower failure rates.8 Implants (failure rate of 0.05 per 100 women per year with typical use) and injectable preparations (3) are among the most effective reversible contraceptives.8 According to recently updated WHO recommendations, depot medroxyprogesterone acetate may be given up to four weeks late without pregnancy needing first to be ruled out.5

How is the effectiveness of hormonal contraceptives affected by drug interaction?

The efficacy of hormonal contraceptives may be reduced when liver enzyme inducing drugs are taken simultaneously.5 Box 1 lists several drugs that interact with hormonal contraceptives. Certain antibiotics without liver enzyme inducing activity alter the enterohepatic recirculation of sex steroids and thereby reduce the efficacy of combined oral contraceptives. Additional contraceptive protection, such as a barrier method, should be used concurrently and for four weeks after discontinuing such drugs. Interactions of antiretrovirals with hormonal contraceptives are specific to the type of antiretroviral and hormonal contraceptive being used. HIV positive women should use a dual method of hormonal and barrier contraception.9

What are the non-contraceptive benefits of combined contraceptive pills?

Analysis of data from 45 observational studies from 21 countries showed that the overall relative risk of ovarian cancer decreased by 20% for each five years of use.10 In women who had used combined oral contraceptives for 15 years the risk was halved. A protective effect with regard to both endometrial and ovarian malignancy can be detected in ex-users of contraceptives for up to 15 years.

Hormonal contraceptives may be used to treat dysfunctional uterine bleeding, dysmenorrhoea, and menorrhagia; their use is associated with a lower incidence of functional ovarian cysts, benign breast disease, and colorectal cancer.^w1 Their effect on bone mineral density depends on the dose of oestrogen and the age of the woman.

What are the adverse effects and complications of hormonal contraceptives?

The side effects and complications of combined oral contraceptives have been well investigated. A nationwide prospective study carried out in the United States showed that after six months of using an oral contraceptive 16% (switchers) to 32% (starters) of women had stopped taking their pill. Nearly half (46%) of the women who discontinued did so because of side effects, such as breakthrough bleeding and headache.11

Case-control studies have shown an increased relative risk of deep venous thrombosis and pulmonary embolism, ranging from 2.1 to 4.4.12 This risk is related to the dose of oestrogen and the type of progestogen. Pills containing desogestrel or gestodene are associated with a twofold greater risk than those containing levonorgestel or norethisterone; those containing cyproterone acetate have a four times greater risk.12 The data are insufficient to make conclusions about combined oral contraceptives containing other progestogens.12 Women with thrombophilia are particularly at risk of thromboembolic events. A systematic review and meta-analysis of seven studies of women taking combined oral contraceptives found significant associations of the risk of thromboembolism with deficiencies of antithrombin, protein C, or protein S; raised concentrations of factor VIIIc; and the presence of factor V Leiden and prothrombin G20210A.13

Use of combined oral contraceptives is associated with an increased risk of myocardial infarction, stroke, gallbladder disease, hypertension, glycometabolic imbalance in people with diabetes, carcinoma of the cervix, hepatocellular carcinoma, and—to a lesser degree—breast cancer in current users. These risks are not modified when ethinylestradiol is given parenterally, or by the use of new progestogens not derived from 19-nortestosterone.5 A Cochrane review found that transdermal patches cause more, and the vaginal ring causes fewer (except for vaginal discharge and vaginitis), side effects than combined oral contraceptives.7 A cohort study found a more than twofold increase in deep venous thrombosis and pulmonary embolism in users of transdermal contraceptives compared with women taking a combined oral contraceptive containing 35 µg ethinylestradiol and norgestimate.14 Box 2 lists contraindications to the use of combined hormonal contraceptives.

The use of a progestogen only is commonly associated with altered bleeding patterns.^{w2 w3} Use of depot medroxyprogesterone acetate decreases bone mineral density, but this returns to baseline values after discontinuation of treatment.^w4

How do intrauterine contraceptives work?

Copper bearing intrauterine devices act by immobilising sperm in the uterine cavity and preventing fertilisation. Of all contraceptive methods, these devices combine the highest efficacy with the lowest cost.^w5 The TCu-380A is approved for 10 years but could be effective for 12.

The levonorgestrel releasing intrauterine system causes marked (but reversible) atrophy of the endometrium. A Cochrane review of contraception trials found this system to be as effective as the TCu-380A.15 It is approved for five years of use and is successful in treating menorrhagia and dysmenorrhoea. A systematic review of nine studies showed that menstrual bleeding over time is reduced by 74-97%.16 A systematic overview of observational studies found limited evidence that this system benefits women with endometriosis, adenomyosis, fibroids, endometrial hyperplasia, and early stage endometrial cancer (in women unfit for surgery).17 WHO guidelines state that fertility returns immediately after removal of all intrauterine contraceptives.4

What are the adverse effects and complications of intrauterine contraceptives?

Insertion of intrauterine devices can be painful. Rarely, uterine perforation occurs. Immediate postpartum or postabortum insertion has the advantages of high motivation, assurance that the woman is not pregnant, and convenience, but it is associated (particularly postpartum and after a second trimester abortion) with a higher expulsion rate than after interval insertion (box 3).5

Copper bearing intrauterine devices increase menstrual flow by 30% on average and may aggravate dysmenorrhoea. According to a recent Cochrane review, non-steroidal anti-inflammatory drugs reduce bleeding and pain associated with the use of intrauterine devices; tranexamic acid is a second line treatment for excessive bleeding.18 A case-control study found that intrauterine devices do not raise the risk of tubal occlusion in nulligravid women,19 and a meta-analysis of case-control studies showed that ectopic pregnancy is not more common in women who conceive with an intrauterine device in place.20 According to observational evidence, intrauterine devices do not increase the risk of pelvic inflammatory disease unless inserted in women with pre-existing gonorrhoea or Chlamydia infection.^w6

Women using a levonorgestrel releasing intrauterine system may have spotting and bleeding during the first months, acne (if already prone to it), mastalgia, or mood changes and they may develop functional ovarian cysts. The recurrence or persistence of side effects may require the removal of the device. Amenorrhoea occurs in about 20% of women one year after insertion of the levonorgestrel releasing intrauterine system. Women may consider it a reason for discontinuation if they were not counselled about the beneficial effect this may have on their health.

How useful are spermicides, used alone?

Spermicides are usually used with barrier devices, and they are not reliable if used alone, except in women whose natural fertility is reduced, particularly with increasing age. Their use many times a day (for example, by professional sex workers) may cause damage of the vaginal wall and facilitate HIV transmission.^w7

Is the “lactational amenorrhoea method” reliable?

The lactational amenorrhoea method is an efficient physiological tool for spacing births. Suckling an infant reduces the release of gonadotrophins, which suppress ovulation and cause amenorrhoea. Reduced suckling leads to the return of ovulation.

For this method to be successful three conditions must be met: the baby must be exclusively or nearly exclusively breast fed on demand, day and night; the mother must be amenorrhoeic; and the method must not be relied on for more than six months. Another contraceptive method must be used as soon as these criteria are no longer fulfilled.

A Cochrane review established that the lactational amenorrhoea method, when correctly applied, is 98% effective.22 The beneficial effects of exclusive breast feeding on the infant are important additional advantages.^w8

When and how to use emergency contraception

Emergency contraception includes all methods that act after intercourse but before implantation. For maximal efficacy it should be used as soon as possible. Combined oral contraceptives, progestogen-only pills, mifepristone, and copper bearing intrauterine devices may be used. Hormonal emergency contraceptives can be offered at any time during the menstrual cycle, and even twice in a given cycle, if necessary.

Currently, the levonorgestrel-only emergency contraceptive is the most widely used. A recent Cochrane review found it to be more effective and better tolerated than the combined oral contraceptive, with no adverse effect on pregnancy.23 A single 1500 µg dose regimen is simpler than 750 µg taken twice, 12 hours apart. When dedicated emergency contraceptive pills are not available, the Yuzpe method may be used: two tablets of a combined oral contraceptive, each containing 50 µg ethinylestradiol and 250 µg levonorgestrel, are taken twice at a 12 hour interval. The selective progesterone receptor modulator mifepristone (10 mg taken within five days of unprotected coitus) is also effective, but it may cause the next menstruation to be delayed,24 which may increase anxiety.

A WHO multicentre randomised trial found that a single low dose of mifepristone and both the single and the two dose regimens of levonorgestrel are equally efficacious.25 A Cochrane review using information from eight randomised controlled trials found that advance provision of hormonal emergency contraceptives had no negative effect on sexual and reproductive health behaviours and outcomes.26 Another systematic review showed that increased access to emergency contraceptive pills enhances use but does not reduce rates of unintended pregnancy.27

Postcoital (up to five days) insertion of a copper intrauterine device prevents implantation. The method is effective, even after multiple coital exposures during a short interval, and it has the advantage of providing ongoing contraception.

What are the drawbacks of sterilisation?

According to the guidelines of the International Planned Parenthood Federation, voluntary sterilisation should be available to all people who do not request it under duress, who are certain that they want no more children, and who understand the nature of the procedure after counselling. Verbal counselling must be backed by printed information to be read by the patient before the operation.^w9

Female sterilisation is more risky than vasectomy. A large prospective multicentre cohort study showed that the cumulative probability of regret within 14 years after tubal sterilisation was considerably higher (20% v 6%) for women sterilised at the age of 30 or less than for those over 30.28 Regret is more common after sterilisation immediately post partum or after an abortion than at a less emotional time. Unpredicted life events, like a change in marital status or the death of a child, are also sources of regret. Counsellors must mention that tubal occlusion is permanent and irreversible, and that it carries a low failure rate.

At what age can a woman stop using contraception?

Women who smoke and those with other cardiac risk factors should discontinue use of combined oral contraceptives at age 35 and switch to another method. In healthy non-smokers, any method that is well tolerated, including low dose (20 µg ethinylestradiol) combined oral contraceptives, can be used up to age 51, after which the risk of conceiving is negligible. Women who prefer to stop using hormonal or intrauterine contraceptives at an earlier age can use a barrier method until menopause is confirmed.