 Nausea and vomiting of pregnancy NVP affects up to 80 of pregnant women, persists throughout pregnancy in 20 of women. 1-3 of pregnant women experience the extreme form called hyperemesis gravidarum HG, described as intractable vomiting associated with weight loss of more than 5 of pre-pregnancy weight, dehydration and electrolyte imbalances which may lead to hospitalization. Treatment involves administration of antiemetics once NVP occurs. Although there is wide evidence of fetal safety of several antiemetic medications, women and health professionals are often reluctant to use antiemetics due to a heightened misperception of teratogenic risk. Diclectin is a prescription drug in Canada specifically indicated for treatment of NVP. Our preliminary research has shown Diclectin to be effective for pre-emptive treatment for NVP symptoms in women who experienced severe NVPHG in their previous pregnancy. This study will evaluate the effectiveness of Diclectin as a pre-emptive treatment for NVP and HG in a randomized controlled trial. In the Pre-emptive Treatment Group, as soon as a patient becomes aware of the present pregnancy, and before the NVP starts, she will take an initial Diclectin dose, followed by standard dosing to match symptoms once NVP develops. In the Standard Treatment Group women will take Diclectin only at appearance of symptoms. A natural history control group will also be included. This study will determine whether pre-emptive use of Diclectin will reduce the incidence of severe forms of this syndromeHG. 