As the incidence of genital HSV infection has increased, the rate of neonatal HSV infection has also risen. The incidence of neonatal herpesvirus infection increased from 2.6 to 11.9 cases per 100,000 live births from 1966 to 1981, according to reports from the United States, where the number of newly diagnosed HSV infections increased tenfold from 1966 to 1995. The incidence of HSV infection at the point of detection by cytology or culture in asymptomatic women at prenatal examination was 0.5% to 1%. The prevalence of HSV-2 antibodies increased by 30% from the period 1976-1980 to 1988-1994. The prevalence of positive HSV-2 antibodies was higher in women than in men. The HSV seroprevalence among pregnant women in the United States is 16.5% to 32%, and most of these individuals are unaware that they have genital herpes. In a US report on neonatal HSV infection, the majority of mothers of HSV-infected newborns were young (mean 21.2 years), 63% of them were white, and 73% were primiparous. Herpes simplex virus (HSV) infection during pregnancy is of concern for two reasons.
1. primary HSV infection during pregnancy can cause spontaneous abortion
2. maternal HSV infection detoxification during delivery can cause life-threatening infection in the newborn.
The natural course and presentation of genital HSV infection during pregnancy.
1, primary HSV infection in women is characterized by
(1) a clinical course of about 3 weeks; (2) massive detoxification from vulvar and cervical damage; (3) enlarged inguinal lymph nodes; (4) often systemic symptoms suggestive of viremia, most episodes of primary HSV infection are asymptomatic or only mildly symptomatic.
2. Effects of HSV infection on pregnancy.
(1) primary genital HSV infection at the time of pregnancy has more adverse effects on pregnancy than the first episode of non-primary genital herpes or recurrent genital herpes.
(2) HSV infection of the fetus through the placenta at the time of initial viremia is rare, so that a diagnosis of congenital infection is uncommon and has been reported in only 8 of 210 (4%) HSV-infected neonates
(3) Symptomatic primary genital herpes in pregnancy is associated with a significant increase in miscarriage, preterm delivery and low birth weight babies. nahmias reported a spontaneous abortion rate of 54% in women with primary genital herpes before 20 weeks of gestation and 35% of babies born to women with symptomatic primary genital herpes after 20 weeks of gestation weighed <2500g and 50% developed neonatal herpes. In another report, of 15 cases of primary genital herpes in pregnancy, 6 (40%) were associated with severe perinatal disease (preterm birth, growth retardation, or neonatal HSV infection). In contrast, the incidence of preterm birth or fetal growth retardation was not increased in pregnant women with recurrent genital herpes.
(4) More detoxification in women with recent HSV infection, more detoxification from the cervix and vulva, and more asymptomatic detoxification.
(5) Asymptomatic detoxification (HSV-2) was detectable in 10.6% of women with symptomatic primary genital herpes in early pregnancy, whereas the detection rate of asymptomatic detoxification in non-primary genital herpes in the first episode of pregnancy was only 0.5%.
In conclusion: the risk of spontaneous abortion and preterm delivery is increased in symptomatic primary genital herpes during pregnancy, but not in pregnant women with recurrent genital herpes. Women with asymptomatic seropositive transmissions occurring late in pregnancy also had an increased risk of preterm delivery. Pregnant women in both groups mentioned above also had an increased risk of transmitting HSV to their newborns.
Risk of neonatal transmission.
1. Most neonatal HSV infections are transmitted through the mother’s birth canal during delivery, and 86% of these are HSV-2.
Up to half of neonates with HSV infection have a mother with primary HSV infection in late pregnancy.
3, Whitley et al. observed that 41% of HSV-infected newborns had a birth weight <2500g, and 51% had no anti-HSV antibodies in their first serum specimen.
4,. The risk factors for HSV infection in neonates are likely to be primary genital HSV infection for the following reasons.
(1) prematurity associated with primary infection.
(2) High detoxification of the birth canal.
(3) Extensive cervical invasion.
(4) Viraemia can occur in the mother.
(5) absence of anti-HSV antibodies in the mother and immature immune function of the infant
(6) The risk of HSV infection in the newborn after the mother’s first HSV infection at the time of pregnancy is much greater than at the time of recurrence. It has been reported that 44% (19/43) of infants born to pregnant women who were first infected with genital herpes at the time of delivery developed neonatal HSV infection, while the incidence of neonatal HSV infection in infants born to women with recurrent genital herpes who delivered with positive HSV cultures was 1/34 and 0/34.
5. Infants born to mothers with recurrent HSV-2 infection have a lower risk of HSV infection, especially invasive disease, because of the protective immunity they receive from the mother.
Although only 10% of women have primary HSV infection at the time of pregnancy, 35% to 50% of neonatal HSV infections are associated with primary infection in the mother. Therefore, prevention of neonatal HSV infection must prevent primary HSV infection at the time of delivery, and also detect and prevent recurrence of genital herpes at the time of delivery.
7. The risk of neonatal infection in pregnant women with primary genital herpes who give birth at term is related to the route of delivery and the duration of rupture of membranes. About 50% of newborns exposed to mothers with the disease were delivered vaginally, while only 1/16 (6%) of newborns delivered by cesarean section (time to rupture membranes <4h) were infected, and 6/7 newborns were infected regardless of the route of delivery if the time to rupture membranes was >4h.
8. The susceptibility to HSV infection during the neonatal period, which can last for several months, may be related to the poor cellular immune response against HSV during this period.
Preventive measures (detection of cases and management)
1. Since it is impractical to routinely screen all pregnant women who deliver for HSV, the current strategy to prevent HSV infection in newborns is to.
(1) Prevention of primary genital herpes at the time of pregnancy.
(2) clinical and virological surveillance of high-risk women close to delivery
(3) timely detection of clinical manifestations of genital herpes in pregnant women near delivery.
(2) During antenatal examination, it is required to record any history of genital herpes in pregnant women or their sexual partners and to evaluate their current sexual behavior. Pregnant women without a history of genital herpes but whose sexual partners have a history of genital herpes or risky sexual behavior should be advised to use condoms during sexual intercourse during pregnancy.
3. Women at high risk of developing primary or recurrent genital herpes should be carefully observed for clinical evidence of genital damage, and those without herpes damage at delivery may deliver vaginally.
4, At delivery or at rupture of membranes, if recurrent herpes damage exists in the genital tract, cesarean delivery can reduce the risk of HSV infection in the newborn, preferably within 4-6h after rupture of membranes.
5. Women who have their first symptomatic episode of HSV infection in the second half of pregnancy should figure out whether it is a recurrence or a true first episode. If the latter, cervical and vulvar HSV cultures should be performed once weekly during the last 6-8 weeks of pregnancy. If there is persistent or frequent asymptomatic detoxification, there is a high risk of detoxification at delivery and cesarean delivery may be an option. If the culture is negative several times and there is no disease damage at the time of delivery, vaginal delivery is possible.
6. The management of pregnant women with HSV damage and early premature rupture of the amniotic membrane should be treated individually. If the pregnancy reaches 34 weeks or more, a cesarean section should be performed as soon as possible. At less than 34 weeks, the risk of preterm delivery and intrauterine infection or neonatal infection must be weighed against gestational age, maternal antibody status, and other clinical factors. Acyclovir, either intravenous or oral, should be considered. Although primary genital herpes in early pregnancy can cause spontaneous abortion, congenital infection is uncommon; therefore, therapeutic abortion is not recommended.
7. If the primary infection occurs at or near term and there is genital herpes damage at the time of rupture of membranes or at delivery, a cesarean section should be performed (if membranes are broken <4h).
8. Mothers with primary genital herpes who deliver vaginally are at particular risk of invasive infection and should be treated early with acyclovir.
9. Hospital staff and other patients should be prevented from having medical-acquired infections. Patients with active damage or positive HSV cultures should live in a single room and use a single bathroom. Staff should wear gloves, isolation clothing, etc.