Purpose: The authors present the case of a woman in the 20th week of pregnancy with herpes simplex virus (HSV)-related gingivostomatitis. They also provide information regarding the benefits and risks of acyclovir, valacyclovir, famciclovir, and shared decision-making (SDM) through which valacyclovir was selected. Case Report: A 26-year-old primigravida woman who denied having a history of systemic diseases presented with fever, general malaise, and abdominal pain at 20 weeks of gestation. As no strong evidence supports any current treatment for primary maternal HSV-1 gingivostomatitis during pregnancy, the authors used three key steps of SDM, namely choice talk, option talk, and decision talk, to help the patient make a decision based on the benefits and ill-effects of treatment with acyclovir, valacyclovir, and famciclovir. Valacyclovir was administered for one week. Her general condition improved gradually, and the symptoms abated without recurrence of fever. Conclusions: Thus, SDM-based treatment was effective in this patient.