Hello, Aciclovir is not licensed for use in pregnancy due to inadequate human studies but is considered safe and has not been associated with an increased incidence of birth defects. Transient neonatal neutropenia19–22 has been reported but no clinically significant adverse maternal or neonatal effects have been reported. Aciclovir is well tolerated in pregnancy. aciclovir in standard doses (400 mg three times daily, usually for 5 days) is associated with a reduction in the duration and severity of symptoms and a decrease in the duration of viral shedding