Background Marginalised populations face significant health risks in pregnancy with reduced access to preventive and life-saving services due to conflict and migration. Infectious disease risk is high and the double burden of malnutrition increases risk from non-communicable disease although only weak epidemiological data supports this in refugees and migrant communities. This manuscript describes the SMRU Refugee and Migrant Pregnancy Cohort commencing nearly 40 years ago, established in response to the very high rate of Plasmodium falciparum maternal mortality in refugee camps on the Thailand Myanmar border Methods Pregnant women who registered to antenatal care clinics of the Shoklo Malaria Research Unit from 1986 to 2024 living in marginalised communities of refugee and migrants were the eligible population. Pregnancies were prospectively followed from enrolment through to childbirth. Types of data include: 1) medical and obstetric records including patient characteristics, pregnancy progress and birth outcomes and 2) investigations (such as HIV). Results Among 94,645 pregnancies maternal mortality was 176 per 100,000 livebirths (120/68,024). Embedded cohorts included observational and clinical trials, providing evidence on the optimisation of treatment of malaria in pregnancy and on the rapid changes towards non-communicable diseases in refugees and migrants. Low mean height (151.4 cm), well below European and American populations from which the majority of guidelines have been created, questions appropriateness, such as gestational weight gain in pregnancy. A broad scope of research findings including tropical infections impacting pregnancy outcomes, mental health and suicide, a shared platform of “-omics” of Karen and Burmese women from first trimester, and practice of care in low-income settings have emerged and been shared. Conclusions The SMRU Refugee and Migrant Pregnancy Cohort findings have had significant local and international impact including changing the World Health Organisation Malaria Treatment Guidelines in pregnancy; and establishing a range of guidelines and tools improving maternal-child health practices.