There is increasing evidence for the use of Steroids for the treatment of the more severe end of the Nausea and Vomiting spectrum, know as Hyperemesis Gravidarum. Steroids have been used for a number of years in pregnancy for conditions such as acute asthma and Crohns disease. There may be a small increased risk of oral clefting associated with the use of corticosteroids and many authorities say that they should not be used to treat nausea and vomiting in pregnancy in the first 12 weeks of pregnancy, however, recent more recent studies are questioning this. There is emerging data on the effectiveness of corticosteroids to treat severe and persistent nausea and vomiting in pregnancy and hyperemesis gravidarum. Corticosteroids need to be given under medical supervision and assessment. They are normally started in hospital Intravenously at a high dose and then tapered off over a number of weeks.
If your hyperemesis is so severe that you are considering termination of the pregnancy then your doctor should be willing to try steroids first.
Taylor R. 2009 Termination is not the Treatment of Choice for Severe Hyperemesis Gravidarum: Successful Management using Prednisolone. Obstetric Medicine 2009; 2: 34–37.