Extreme heat exposure is associated with adverse outcomes in pregnancy and has the potential to impact maternal, neonatal and child health for a lifetime. In an extremely hot climate, pregnant women face an increased risk of premature birth, stillbirth, low birth weight, congenital anomalies and pre-eclampsia. In low- and middle-income countries (LMICs), socio-demographic and behavioural practices may negatively affect body hydration during high temperatures. The possible causes and consequences of dehydration in the heat are poorly understood and have been little discussed in the literature.Living in a hot climate poses various challenges, including dehydration, where biological mechanisms and insufficient access to water can lead to dehydration in women and children, with consequences for the health of both mothers and children, particularly in relation to breastfeeding habits. During pregnancy, increased metabolic and cardiovascular demands interact with heat exhaustion and reduced availability of fresh water, which can affect the child’s growth and development. In this opinion piece, we emphasise the possible causes and impacts of dehydration in extreme heat on the health and well-being of mothers and children. We encourage more research, focused on biology and epidemiology, related to raising awareness and implementing adaptations to reduce the risk of dehydration in pregnant, postpartum women and newborns in the context of climate change-related heat exposure.