Updated guidelines for treating nausea and vomiting during pregnancy. Good scientific evidence supports using vitamin B₆ (pyridoxine) alone or with added doxylamine as first-line therapy in the treatment of nausea and vomiting during pregnancy, according to an update from the American College of Obstetricians and Gynecologists. Recommendations include starting prenatal vitamins one month before becoming pregnant, if possible, which may reduce nausea and vomiting. Limited scientific evidence supports using ginger for relief of nausea and methylprednisolone as a last resort for severe nausea and vomiting. Patients with clinical signs of dehydration may benefit from intravenous hydration. Peripherally inserted central catheters are a last resort for women with hyperemesis gravidarum. The advice, released in January, is summarized in Practice Bulletin No. 189, which replaces Practice Bulletin No. 153 from September 2015.