Viral Infections in Pregnancy & Neonate

Viral infection of the fetus and newborn is common, and it often hides inside other problems: poor intrauterine growth, an unexplained rash or low platelet count, or a baby who looks septic but grows no bacteria. The decisive variable is timing. A virus reaching the fetus during organogenesis tends to deform; the same virus acquired around delivery tends to overwhelm a newborn with no immunological memory and little transferred antibody; a virus acquired after birth is usually milder. Knowing when a virus was acquired predicts both the agent and the pattern of harm.

Two principles run through the topic. The old TORCH grouping (toxoplasmosis, other, rubella, cytomegalovirus and herpes simplex virus) has outlived its usefulness, because each agent has a distinct clinical signature, a distinct test and, increasingly, a distinct treatment. And diagnosis in the infant is virological, not serological: maternal antibody crosses the placenta, so a positive antibody result in the baby usually reflects the mother’s past exposure rather than the baby’s own infection.

These articles work through the topic.

→ See Viral Infections of the Fetus and Newborn for the framework of vertical transmission and the agent-by-agent account: recognising congenital infection, then herpes simplex, varicella-zoster, cytomegalovirus, rubella, parvovirus B19, the neonatal enteroviruses, and the bloodborne hepatitis viruses and HIV.

→ See Cytomegalovirus in Pregnancy and the Newborn for the in-depth clinical account of the commonest congenital infection: risk by serostatus and gestational age, diagnosis in the mother, fetus and newborn, the maternal valaciclovir and neonatal valganciclovir regimens, and the South African burden.

Congenital and perinatal viral infections at a glance

Virus	When the danger lies	Fetal or neonatal disease	Prevention
Cytomegalovirus	Prenatal	Congenital cytomegalovirus: sensorineural deafness, neurodisability	Hygiene advice; no vaccine
Rubella	Prenatal, first trimester	Congenital rubella syndrome: deafness, cataracts, heart disease	Measles-rubella vaccine before pregnancy
Varicella-zoster	Prenatal and perinatal	Congenital varicella syndrome; severe neonatal varicella	Childhood vaccine; varicella-zoster immunoglobulin after exposure
Herpes simplex	Perinatal	Neonatal herpes: skin-eye-mouth, neurological and disseminated disease	Caesarean for active lesions; neonatal aciclovir
Parvovirus B19	Prenatal	Fetal anaemia and hydrops	None; intrauterine transfusion treats hydrops
Zika	Prenatal	Congenital Zika syndrome: microcephaly	Avoid exposure; vector control
Enteroviruses and parechoviruses	Perinatal and postnatal	Neonatal sepsis, meningitis, myocarditis	Supportive care
Hepatitis B	Perinatal	Chronic infection	Birth-dose vaccine and immunoglobulin
Hepatitis C	Perinatal	Chronic infection, often presenting later	No proven intervention
HIV	Perinatal and postnatal	Paediatric HIV infection	Maternal antiretroviral therapy; infant prophylaxis

Key terms

The vocabulary that recurs across the topic.

Timing of infection:

Term	Definition
Congenital (prenatal)	Acquired in the womb, across the placenta, at any gestation.
Perinatal (intrapartum)	Acquired around the time of delivery, from the birth canal, maternal blood or secretions.
Postnatal	Acquired after birth, through breast milk, contact or respiratory spread.

Recurring signs of congenital infection:

Term	Definition
Intrauterine growth restriction	Poor fetal growth, a common and non-specific marker of congenital infection.
Non-immune hydrops fetalis	Fluid accumulation in fetal compartments without red-cell antibody, classically from parvovirus B19.
Blueberry muffin rash	Blue-red skin nodules of blood formation in the skin, shared by congenital rubella and cytomegalovirus.
Periventricular calcification	Calcium deposits around the brain ventricles, characteristic of congenital cytomegalovirus.

References and recommended reading

• Schleiss MR, Marsh KJ. Viral Infections of the Fetus and Newborn. In: Gleason CA, Juul SE, editors. Avery’s Diseases of the Newborn, 10th edition, Chapter 37. Elsevier; 2018. The principal source for the timing-based framework of fetal and neonatal viral infection and the agent-by-agent congenital and perinatal syndromes summarised here.