The risk of transmission of recurrent genital herpes to the fetus is considerably lower than that of primary genital herpes, with a lower risk of disease transmission to the newborn in mothers with recurrent genital herpes during pregnancy or in mothers with primary HSV infection during the first half of pregnancy (<1%) and a higher risk of disease transmission to the newborn in mothers with primary HSV infection near the time of delivery (30%-50%). Spontaneous abortion, intrauterine growth retardation, preterm birth, low birth weight and congenital malformations of the infant, such as microcephaly, microphthalmia, abnormal retinal development and cerebral calcification, can occur in pregnant women with primary HSV infection in the early stages of pregnancy (first trimester) and in fetuses infected through the intrauterine placenta, but few cases of transplacental infection have been reported in the literature. Recurrent genital herpes in pregnant women is less likely to cause neonatal HSV infection and is not associated with preterm birth or low birth weight. Most mother-to-child transmission occurs when the fetus passes through the birth canal; infection of the fetus through the placenta is rare. During pregnancy, mothers should avoid unprotected genital and oral sexual contact with sexual partners who have HSV infection, suspected infection, or whose infection status is unknown. Pregnant women with primary HSV infection within 4 weeks prior to delivery have a higher likelihood of neonatal herpes infection and may be considered for cesarean delivery as well as for prophylactic treatment with acyclovir. The use of drugs such as acyclovir in pregnant patients is controversial. The use of antiviral therapy in pregnant women should be weighed against the pros and cons, and fully informed consent should be obtained from the pregnant woman. Female patients on long-term suppressive therapy who are intending or already pregnant are advised to discontinue antiviral therapy. In pregnant women with primary or incipient genital herpes, acyclovir 400 mg orally three times daily is recommended; in cases of severe complications that may be life-threatening, acyclovir should be administered intravenously. Intermittent treatment or suppressive therapy in early pregnancy should be avoided in cases of early relapse. If treatment must be given because the patient is ill or has complications, drugs other than acyclovir should be avoided and the acyclovir dosage should be controlled to the minimum effective dose. In pregnant patients with frequent recurrent or recent genital herpes infections, acyclovir treatment may be used near term to reduce the appearance of active damage and thus reduce the rate of cesarean delivery. Pregnant women with a previous history of recurrent genital herpes but no signs of recurrence near term may be treated without acyclovir. In pregnant women with active lesions or prodromal symptoms, cesarean delivery may be performed before rupture of membranes, provided there are no contraindications, but cesarean delivery does not completely prevent the development of herpes in the newborn. Pregnant patients without active lesions can be delivered vaginally, but their newborns should be monitored closely after delivery for fever, lethargy, weak sucking during breastfeeding, convulsions, or occurrence of lesions for timely management. For infants with neonatal herpes, acyclovir 20 mg/kg, d, intravenously, every 8 hours, for a course of 21 d if the infection is disseminated or involves the central nervous system, or 14 d if it is confined to the skin mucosa.