The interconnectedness of the global HIV and sexually transmitted infection (STI) epidemics necessitates integrated strategies to address both. This Series paper highlights the biological link between HIV and STIs, and describes the successful progress in HIV response versus STI response over the past decades. The concept of undetectable=untransmissible (U=U) in HIV treatment has revolutionised HIV prevention by reducing stigma and promoting early treatment. In line with this approach, we discuss the role of chronic suppressive therapy for herpes simplex virus type 2 and the importance of the accurate diagnosis and treatment of curable STIs to prevent transmission between sexual partners. This Series paper explores the potential of pre-exposure prophylaxis (PrEP) for HIV in different forms (eg, daily oral PrEP, event-driven PrEP, and long-acting injectable PrEP), and highlights the challenges of adherence to daily regimens and the promise of longer-acting agents, such as cabotegravir and lenacapavir. The potential of doxycycline post-exposure prophylaxis for the prevention of bacterial STIs is also discussed, with concerns about antimicrobial resistance. Although vaccine development for HIV and STIs is a key biomedical advance, we discuss the challenges and possibilities of developing effective vaccines, including lessons learnt from previous HIV vaccine trials, the potential of mRNA-based vaccines for herpes simplex virus, ongoing trials for gonorrhoea and chlamydia vaccines, and the impact of existing human papillomavirus and mpox vaccines. Diagnostic innovations emphasise the importance of point-of-care tests for HIV and STIs. This Series paper discusses the benefits, landscape, and pipeline of rapid diagnostic tests (eg, lateral flow tests and molecular assays) and the challenges of implementing these tests in low-resource settings, particularly the need for rapid results to inform clinical decisions, promote convenience, and reduce cost. This Series paper also addresses innovations in service delivery and advocates for integrated and person-centred approaches (eg, differentiated services) that combine HIV and STI services, and highlights the potential of community-based and home-based models to improve access and reduce stigma.

Contraception and family planning are vital aspects of sexual and reproductive health and rights. Despite major advances in modern contraception over the past 60 years many gaps remain, and the rate of unplanned pregnancies and abortions remains high. These issues have given rise to a new era in contraception research with great opportunities and many challenges. These opportunities include new innovations, particularly in the areas of male contraception, non-hormonal female contraception, and multipurpose prevention methods that provide contraception in combination with protection against leading sexually transmitted pathogens; fast tracking new inventions currently in the pipeline by intensifying support from government, non-profit, and industry entities; the provision of new methods, services, and messaging for underserved populations including men, marginalised women, and transgender individuals; and better understanding the needs of diverse populations. Major challenges in contraception research include inertia, especially in industry involvement; a new wave of conservatism and government interventions that threaten to impede contraception development, services, and education; and understanding what people want and how to provide solutions. The best way to improve family planning and promote women's health is to offer better contraception options to those who wish to avoid unplanned pregnancy. This can be done by renewed commitment from scientists, private foundations, and government institutions, and from industry partners who are needed to bring promising developments to market.

The concept of sexual and reproductive health and rights has evolved in the 21st century from previous narrower conceptualisations. In 2018, the Guttmacher-Lancet Commission proposed a broader and integrated defining framework, together with a package of essential health service elements. Despite this, progress on the sexual and reproductive health agenda has been inconsistent, with progress in some areas and considerable gaps in others. Even in areas that have seen breakthroughs in biomedicine and technology, progress has been partial owing to inadequacies in funding, policy, and implementation. Additionally, initial executive orders of the Trump administration in early 2025 presented a major challenge to sexual and reproductive health and rights in the USA, and orders on US foreign aid threaten devastating impacts on sexual and reproductive health and rights in recipient low-income and middle-income countries. As discussions of sexual and reproductive health and rights are often seen to be sensitive or controversial, even when had at a senior government level, any consideration of time trends in sexual and reproductive health outcomes need to consider the complex interplay between trends in social and cultural factors, politics and legal frameworks, and technology and biomedicine. The perceived sensitivity of sexual and reproductive health means that providing adequate education on sex, sexuality, and relationships is crucial, and this education is often resisted by religion or traditionalist sentiments. Furthermore, technological change means that many young people receive this education online, which has both positive and negative effects. A thorough understanding of the driving factors behind global epidemiological trends in sexual and reproductive health-such as fluidity in gender and sexual identity, biomedical innovations in contraception and the treatment and prevention of HIV and other sexually transmitted infections, gender-based violence, access to safe abortion, fertility needs, and comprehensive sexuality education-is crucial in assessing progress on the sexual and reproductive health and rights agenda. To this end, this Series paper provides an overview of trends in sexual and reproductive health and rights outcomes since 2018.

Peripartum cardiomyopathy is increasingly recognised and diagnosed in clinical practice. Over the past two decades, a substantial amount of new knowledge on this condition has been accrued, including a better understanding of the pathophysiology, genetic predisposition for a proportion of patients, diagnostic tools, management with a disease-specific therapy, and predictors of outcome. Peripartum cardiomyopathy occurs globally in all ethnic groups and should be suspected in any women who are peripartum presenting with symptoms and signs indicative of heart failure towards the end of pregnancy or in the months following delivery. Verification of left ventricular systolic dysfunction (ejection fraction <45%) is crucial for the diagnosis of peripartum cardiomyopathy and the exclusion of other causes of heart failure, such as pre-existing cardiomyopathy, valvular heart disease, or congenital heart disease. Peripartum cardiomyopathy is a disease with considerable maternal and neonatal morbidity and mortality, with only half of women experiencing complete myocardial recovery within 6 months of the onset of symptoms. This Seminar summarises current knowledge of peripartum cardiomyopathy genetics, pathophysiology, diagnostic approaches, medical management, and outcome. Furthermore, we provide guidance on both risk stratification by use of a novel score to predict recovery and on the outcomes of a subsequent pregnancy.