Pediatric emergency medicine trisk 2587 2587

transmission in utero (congenital infection) (5%), or while passing through an
infected birth canal (intrapartum) (85%), or from contact with infected oral
secretions (postpartum) (10%).
Maternal HSV infection can be described as first-episode primary infection,
first-episode nonprimary infection, and recurrent infection. First-episode primary
infections occur in mothers who have never been previously exposed to infection.
First-episode nonprimary infections occur when a mother has had HSV-1
previously and then becomes infected with HSV-2 (or vice versa) since HSV-1
and HSV-2 share significant cross reactivity. Recurrent maternal infection implies
that the mother has had a previous exposure and has formed protective antibodies
that are conveyed to the baby but is having a reactivation.
Recurrent infections are responsible for 50% of the cases of neonatal HSV
because recurrent maternal outbreaks occur more commonly than primary
infections. However, primary infections are more severe in nature than recurrent
episodes due to the absence of maternal antibodies and shedding of higher
quantities of HSV for longer periods of time. About 30% of pregnant women will
have serologic evidence of HSV-2, the majority without prior history of
symptoms or infection.
Complete perinatal history may reveal the occurrence of genital outbreaks
before or shortly after birth. History of contact with a person who has had cold
sores or presence of breast lesions in breast-feeding mothers may be helpful.
Maternal history of a genital infection is often unclear due to the possibility of
asymptomatic or subclinical infections. It is estimated that 60% to 80% of women
whose infants develop HSV do not have a prior history of genital infection or
symptoms. Mothers with a history of recurrent HSV infection have a 2% chance
of transmitting infection to their newborn at delivery during active shedding. The
chance of transmission increases to 57% in first-episode primary maternal
infection and 25% in first-episode nonprimary infection. History may also reveal
the presence of risk factors such as a primary infection, vaginal delivery,
prolonged rupture of membranes (>4 to 6 hours), use of fetal scalp electrode, or
disruption of the skin during vacuum extraction.

HSV disease in neonates is usually symptomatic. It can present in two forms:
(a) Congenital HSV infection from an in utero transmission (characterized by
vesicular skin lesions, or scarring, neurologic lesions [microcephaly,
hydranencephaly, intracranial calcifications, hypertonicity, or seizures] and ocular
findings [chorioretinitis, microphthalmia, cataracts, or optic atrophy]) or (b)
neonatal HSV, which may present 2 to 3 weeks after discharge from the newborn
nursery.