Hyperemesis gravidarum causes severe nausea and vomiting during pregnancy. Even though it affects up to 3 percent of pregnancies, research about its causes and treatments is sparse.
It can be hard to eat a balanced diet when you are suffering from nausea and vomiting. You may only feel like oranges, hot chips, lemonade, ice blocks and pizza.
Professor and Co-Director of the Institute of Metabolic Science and Director of the Medical Research Council Metabolic Diseases Unit, University of Cambridge