Access to sexual and reproductive health services and information, including a comprehensive range of contraceptive methods, is fundamental to the rights and well-being of women and adolescent girls (1–4). There is a wide range of hormonal and non-hormonal modern contraceptive methods providing substantial individual and public health benefits. A core part of the work of the World Health Organization (WHO) is the development and maintenance of up-to-date, evidence-based guidance on contraceptive safety for individuals with particular medical conditions or medically relevant characteristics (5). The Medical eligibility criteria for contraceptive use (the MEC), fifth edition, offers national policy-makers and family planning programmes a comprehensive set of recommendations on the medical safety of contraceptive methods, allowing for the informed development of national policies, protocols and programmes (5). Global guidance about medical safety and eligibility facilitates the removal of unnecessary medical barriers to contraception.

For over 20 years, the MEC has been used by countries to maximize safety and improve the quality of contraceptive care offered. Guidance about safety is kept up to date through continuous monitoring and reviews of published literature. In 2015, WHO released the fifth edition of the MEC (5). This edition contains more than 2000 recommendations for 25 different contraceptive methods, within the context of more than 80 medical conditions or medically relevant personal characteristics. Depending on the individual, more than one condition may need to be considered when making an informed contraceptive choice (5). The recommendations in the MEC are based on several considerations, including whether the use of a contraceptive method worsens the medical condition or creates additional health risks, and whether the condition makes the contraceptive method less effective (5).

The MEC is part of a set of tools aiming to improve contraceptive coverage and care throughout the world. The MEC informs decisions about who might use a particular contraceptive method, through information and guidance about the safety and appropriateness of contraceptive care. The Selected practice recommendations for contraceptive use (the SPR) provides guidance on how to safely and effectively use various contraceptive methods (6). WHO produces a range of tools to support the use and implementation of contraceptive guidance, such as the MEC wheel and the Global handbook for providers (7, 8).

Since 1996, the MEC has applied a four-category scale to indicate medical eligibility for particular contraceptive methods in the presence of particular conditions or individual characteristics (e.g. at high risk of HIV). For each condition or characteristic, contraceptive methods are placed into one of four numbered categories:

1. A condition for which there is no restriction for the use of contraceptive method.
2. A condition where the advantages of using the method generally outweigh the theoretical or proven risks.
3. A condition where the theoretical or proven risks usually outweigh the advantages of using the method.
4. A condition which represents an unacceptable health risk if the contraceptive method is used.

In the past, there has been mixed evidence about whether hormonal contraceptive methods – particularly depot medroxyprogesterone acetate (DMPA) – are associated with an increased risk of HIV acquisition. The available evidence consisted of theoretical biological data and observational studies with important limitations. In 2016, the independent Guideline Development Group (GDG) for the MEC reviewed the accumulating evidence regarding women at high risk of acquiring HIV (9). The GDG concluded that there remained uncertainty about whether the increased risk of HIV acquisition seen in some observational studies was a real effect of the contraceptive method used or whether it was a statistical artefact resulting from key limitations of observational studies (residual confounding in particular) (9). There also continued to be uncertainty about the clinical relevance of the biological data. In addition, there was concern that previous attempts to inform women of the uncertainty about both the epidemiological and biological data (through the use of a MEC clarification, indicated by an asterisk [*]) had not been effective. Given these concerns, the GDG concluded that MEC guidance should be changed. Thus, in 2017, the recommendation for progestogenonly injectable use among women at high risk of HIV infection was changed from MEC Category 1* (no restrictions to use, with a clarification) to MEC Category 2 (the benefits of use outweigh the risks), with an accompanying clarification (9).

This new classification indicated that progestogen-only injectables could be used by women at high risk of HIV, because the advantages of these methods generally outweighed the possible disadvantages, and it highlighted that, when choosing these methods, there might need to be extra consideration of possible HIV acquisition, and counselling.

As part of the 2017 revision, WHO reaffirmed its commitment to monitoring and assessing any new evidence relevant to contraceptive safety. New information, including results from a large, multinational randomized controlled trial (RCT) (10), led WHO to convene another GDG meeting in July 2019 to review all the available evidence and assess whether the MEC guidance needed revision.