Objectives. To determine whether the initiation of treatment (preemptive treatment) before the symptoms of nausea and vomiting of pregnancy (NVP) versus when the symptoms begin can improve the outcome in patients at a high risk for recurrence of severe NVP. Study Design. Prospective, randomized controlled trial. Results. Preemptive therapy conferred a significant reduction in HG as compared to the previous pregnancy (P = 0.047). In the preemptive arm, there were 2.5-fold fewer cases of moderate-severe cases of NVP than those in the control group (15.4% versus 39.13%) in the first 3 weeks of NVP (P = 0.05). In the preemptive group, significantly more women had their NVP resolved before giving birth (78.2% versus 50%) (P < 0.002). Conclusions. Preemptive treatment with antiemetics is superior to the treatment that starts only when the symptoms have already occurred in decreasing the risk of severe forms of NVP.