Given their high risk of HIV and unintended pregnancy, female sex workers (FSWs) have high and sustained risk of vertical transmission of HIV during pregnancy, delivery or breastfeeding. Prevention of Mother To Child Transmission (PMTCT) is a four-prong approach to reducing vertical transmission. It includes HIV prevention in women of childbearing age, utilisation of family planning services for HIV infected women, completion of the PMTCT cascade (ANC attendance, HIV counselling and testing, ART for infected mother, ARV prophylaxis and correct feeding practices for the for uninfected infant) and providing care, ART and support to HIV-infected mothers and their children who are living with HIV. Paper A reports on results of a multivariate logistic regression carried out on routine clinic data from drop-in centres serving FSWs in Kilifi and Mombasa counties in Kenya. The analysis found high utilisation of family planning but relatively low utilisation of PrEP. Overall, FSWs with more selfreported sex acts per week and thus higher risk for pregnancy had greater utilisation of family planning suggesting a good level of risk perception. FSWs with more self-reported sex acts per week and thus higher risk for HIV had lower utilisation of PrEP suggesting barriers to acceptability of PrEP. Geographical disparities were noted with odds of PrEP utilisation in Mombasa being higher than in Kilifi reflecting the sparse distribution of facilities offering PrEP in Kilifi and difficulty accessing these clinics due to higher poverty rates. Odds of family planning utilisation in Kilifi was higher than in Mombasa reflecting the secondary benefits of family planning research underway in Kilifi. The analysis found that PrEP utilisation does not appear to vary by the peer educator workload which may suggest PrEP hesitancy and a preference for more familiar HIV prevention methods. Utilisation of family planning was greater amongst those with a higher peer educator workload possibly reflecting understanding of, need for and acceptance of family planning. Paper B reports on findings of in-depth interviews carried out amongst FSWs in Port Elizabeth, South Africa to understand the barriers and facilitators to PMTCT cascade completion, as well as their experiences when participating in a peer mentorship programme. Cascade completion was inhibited by lack of knowledge, low socioeconomic status, substance use, and various intersecting stigmas. Facilitators included support from family and friends, desire to protect their own health and that of their children, and the ease of use of interventions. Benefits of peer education programmes included increased knowledge and utilisation of PMTCT services, personal development, and relationship building between FSWs and with their families. Mentors noted experiencing self-improvement and a sense of fulfilment from participating in the programme, however, being a mentor took an emotional toll and left them with a sense of helplessness when faced with insurmountable mentee challenges. Strategies to increase knowledge and acceptability of interventions include building health literacy to improve individuals’ ability to understand and critically analyse health information, and improving patient-provider dynamics to improve transmission of important information. FSWs’ programmes should include treatment for mental ill-health and substance use, and development of tailored, informed interventions that address the complex and overlapping correlates of psychological morbidity. Health care workers and the community at large should be sensitised on the plight of key populations to reduce stigma, for example through trainings and community health education programmes. Further, advocates should engage decision makers to encourage them to adopt less punitive sex work legislation and, in the case of South Africa, streamline legislation around migrant access to care. The public health system should be strengthened by increasing national funding to address shortages in human resources and improve the quality and accessibility of health facilities. Lastly, peer education programmes should be evaluated to ensure that they are sustainable and transformative, tackling key issues such as self-stigma and financial security.