Maternal and paternal characteristics (for example, maternal and paternal obesity, maternal gestational hypertensive disorders and maternal dietary intakes) are linked with the offspring’s risk of obesity and cardiometabolic disease in adulthood (such as coronary heart disease and type two diabetes). One explanation for such correlations is that maternal and paternal phenotypes alter the environment that the sperm, egg cells and fetus develop in, thereby causing the offspring to be more susceptible to cardiometabolic disease in adulthood. However, mothers and fathers also pass on their genes to their children, and provide an environment for their children to grow up in, both of which provide alternative explanations for the aforementioned correlations. Because of this it is currently unclear whether the mother’s and father’s BMI, maternal gestational hypertensive disorders and maternal dietary intakes have causal effects on the offspring’s risk of obesity and cardiometabolic disease.