Smoking and use of alcohol by pregnant women is associated with many adverse health outcomes for both the mother and baby (e.g., miscarriage, stillbirth, prematurity, low birthweight, sudden infant death, foetal alcohol syndrome). Health policy and interventions in high income countries, such as the UK, have reduced rates of smoking and alcohol use during pregnancy; however, the prevalence of these harmful behaviours in low and middle income countries is rising. We are interested in investigating these health behaviours in Uruguay, where more than a quarter of women smoke throughout pregnancy and nearly half of women use alcohol in pregnancy. Intervening with smoking and alcohol use in pregnancy in Uruguay presents a significant opportunity for reducing these health behaviours in the long-term and for disease prevention. Yet policy on smoking/alcohol and pregnancy in Uruguay is limited and findings from surveys suggest that both the health care system and health professionals in Uruguay have not sufficiently prioritised reducing smoking and alcohol use during pregnancy. Efforts to implement further policy changes have been impeded by insufficient national evidence concerning the harms and economic consequences of these health behaviours. We aim to analyse existing data from national surveys in Uruguay to establish evidence, within the national context, for the relationship between pregnant women’s smoking and alcohol use and the harms to themselves and their infants. Given the existing evidence from countries such as the UK, and, in order to inform health policy in Uruguay, we aim to compare the evidence for these health effects in Uruguay with effects observed in the UK. We hypothesise that the harmful effects of smoking and alcohol in pregnancy in Uruguay will be more pronounced than in the UK; this is because in Uruguay a poorer health care system and high levels of other risk factors (e.g., poor diet, substance misuse) might exacerbate the effects relative to a developed country. We aim to do this using UK data from the Avon Longitudinal Study of Parents and Children (ALSPAC). This study is a collaboration between academic groups in the UK and Uruguay, and The Lullaby Trust, a charity concerned with maternal smoking and use of alcohol as they can lead to sudden infant death. We anticipate that findings from this study will help policy makers and practitioners in Uruguay better understand smoking and alcohol use during pregnancy and its impact on the mother’s and infant’s health. Through this, we hope to directly influence policies and service provision for pregnant women in Uruguay.