An updated practice bulletin from the American College of Obstetricians and Gynecologists urges clinicians to treat nausea and vomiting of pregnancy as early as possible in order to prevent it from progressing to hyperemesis gravidarum. The practice bulletin, published online December 21 and in the January issue of Obstetrics & Gynecology, replaces an earlier one published in September 2015. Level A recommendations include:

• Use of vitamin B6 (pyridoxine) alone or in combination with doxylamine as first-line pharmacotherapy, as they are safe and effective.
• Encouragement of women to take prenatal vitamins for 1 month before fertilization, as it may decrease the incidence and severity of nausea and vomiting during pregnancy.
• Recommendation for supportive therapy for abnormal maternal thyroid tests caused by gestational transient thyrotoxicosis or hyperemesis gravidarum, or both, and recommendation against antithyroid medications.