Nausea and vomiting in pregnancy is very common and affects up to 80% of women. It is usually mild and resolves during the first half of pregnancy. However, in a small proportion of women (0.3–3.6%), symptoms are so severe that they lead to dehydration, electrolyte imbalance and weight loss. This is known as hyperemesis gravidarum. Women who have persistent symptoms into the second trimester of pregnancy should have consultant-led antenatal care and serial fetal growth ultrasound.