This is a multicenter study in the treatment of NVP that will actively recruit pregnant adolescents from approximately 14-16 study sites in the United States. After obtaining informed consent on Day 1, a medical examination will be conducted to ensure eligibility. Participants will be randomized to receive Diclegis or placebo. On Day 1, all participants will take 2 tablets of study drug at bedtime. On Days 2 to 14, participants will take 2 tablets of study drug at bedtime. The minimum dosage will be 2 tablets daily at bedtime, increasing, when indicated, to the maximal dosage of 4 tablets per day on Days 3 to 14. Participants will be required to complete a diary daily to assess the severity of their NVP by using the validated Pregnancy Unique Quantification of Emesis (PUQE) and to record any AEs experienced; the Global Assessment of Well being scale will be completed only on Days 1, 8 and 15. Participants will receive telephone calls daily to assess whether the current dosing regimen is sufficient at relieving NVP symptoms, to review study procedures, and to address her questions/concerns. Participants will return to the clinic for evaluation on Day 4 (±1 day) and Day 15 (±1 day) for an end of study visit.