Climate change has resulted in increased mean temperatures globally. Accompanying this is increased frequency of extreme weather events, including heat waves. Some epidemiological studies suggest that exposure to heat waves in pregnancy are detrimental for fetal outcome. However, evidence for this is limited and yet to be tested experimentally. The aim of this study was to determine, in mice, the impact of heat wave exposure in late gestation on maternal adaptations and fetal and placental development. C57BL/6J female mice were time-mated, with the first day of pregnancy termed as embryonic day (E) 0.5. Dams were randomly allocated to either a control group (standard housing conditions) or a heat wave group (exposure to 36°C for 8 hours from E15.5-17.5). Maternal weight gain, food and water intake, and rectal temperatures were measured daily throughout gestation. Dams were culled on E18.5, and feto-placental units were dissected and weighed. Heat wave exposure decreased maternal weight gain in the last three days of gestation by 65% in comparison to controls. This was accompanied by a 40% decrease in food intake over the same period in the heat wave group. Heat wave exposure also caused maternal behavioural adaptations with significantly increased water intake (41% in comparison to control), rectal temperature (Con: 37.3 ± 0.2; Heat wave: 38.3 ± 0.2), and decreased nest building complexity. Underlying the maternal heat wave response were reductions in fetal weight and placental weight (20% and 15% respectively in comparison to controls). This preliminary data indicates that exposure to heat waves in late gestation alters maternal physiology and behaviour, with detrimental effects on placental and fetal development. Therefore, we need to better understand whether the predicted increase in heat wave events due to climate change should be a concern for human pregnancy.