While a proportion of women with the metabolic syndrome become pregnant, pregnancy itself creates a milieu that is similar to the syndrome, including the development in some women of insulin insensitivity and increased levels of blood glucose, raised triglycerides and high blood pressure. As well as a potential acceleration in the risk of cardiovascular and diabetes-related complications, the appearance of features of the metabolic syndrome in pregnancy may also harm the fetus. David Simmons looks at how the changes in pregnancy can create a heightened susceptibility to potential harm for a mother and her baby.