Changes to the placenta occur as the demands of the foetus increase throughout gestation. It has been established that physical activity performed during pregnancy can benefit both the mother and infant, however the impact of exercise on placental development and maturation is less known. The aim of this systematic review and meta-analysis was to investigate the effect of exercise performed during pregnancy on placental weight and volumetric measures and the placenta weight to birthweight (PWBW) ratio. Six electronic databases (PubMed, Web of Science, Cochrane Central, Embase, SportDiscus and CINAHL Complete) were searched from inception to April 2021 for studies comparing a regular prenatal exercise intervention with either usual maternal care or a lower frequency of exercise for its effect on measures of placental morphological composition. Randomised controlled trials and cohort studies were included in the systematic review and meta-analysis. Statistical analyses were performed for placenta weight, measures of placental volumetric composition, and the PWBW ratio. Seven randomised controlled trials (n=7) and two cohort studies (n=2) were included in the systematic review and all nine studies were included in the meta-analysis (n=9). There was no significant difference in placenta weight or volume between exercise and control groups. Placental functional volume was significantly higher and non-functional volume was significantly lower in women who exercised compared to those that were sedentary during pregnancy. Physical activity performed during pregnancy may not alter placenta weight or placenta volume. However, exercise may optimise the functional units of the placenta through an increase in villous tissue and intervillous space volume and a reduction in non-functional tissue volume. Further research is needed on the effects of prenatal exercise, including different volumes or intensities, on placental villous composition.