11.4 Congenital & Perinatal Infections, Sexually Transmitted Infections and Immune Function
Key Takeaways
- IgG is the only immunoglobulin that crosses the placenta and it transfers mainly in the third trimester — which is why preterm infants are more susceptible and why maternal antibody wanes to a physiologic nadir at 3 to 6 months — whereas IgM does not cross, so elevated IgM in cord or neonatal blood proves the fetus produced its own antibody and establishes an intrauterine infection.
- C-reactive protein begins rising only 6 to 12 hours after inflammation starts, so a normal initial CRP must never be used to withhold antibiotics from a symptomatic infant; serial normal CRPs at 24 and 48 hours are used to stop antibiotics, not to avoid starting them.
- Cytomegalovirus produces periventricular intracranial calcifications while toxoplasmosis produces diffuse scattered calcifications; CMV is the most common congenital infection and the leading non-genetic cause of sensorineural hearing loss, and it must be diagnosed by urine or saliva PCR within the first 21 days of life.
- HIV diagnosis in the neonate requires virologic DNA or RNA PCR testing, never antibody testing, because transplacental maternal IgG produces positive antibody results in uninfected infants for up to 18 months.
- Chlamydial conjunctivitis is not prevented by erythromycin eye prophylaxis and appears later, at day 5 to 14; it requires systemic oral erythromycin or azithromycin, because topical therapy clears neither the nasopharyngeal carriage nor the 4 to 12 week staccato-cough pneumonia that follows.
Last updated: August 2026
11.4 Congenital & Perinatal Infections, Sexually Transmitted Infections and Immune Function
Clinical Pearl & Core Takeaway: The NCC blueprint's Infection and Immunology heading lists antibody function (IgA, IgG, IgM), then names the organisms individually — HIV, cytomegalovirus, rubella, hepatitis B, varicella, toxoplasmosis, herpes, human papillomavirus, enterovirus, group B streptococcus, staphylococcus, E. coli, gonorrhea, chlamydia, and syphilis. Two facts unlock most of this material: IgG is the only immunoglobulin that crosses the placenta, and therefore an elevated IgM at birth proves the fetus made its own antibody — an intrauterine infection.
1. Neonatal Immune Function
The three immunoglobulins
| Immunoglobulin | Crosses the placenta? | Source in the neonate | Clinical meaning |
|---|---|---|---|
| IgG | YES — the only one, by active transport, overwhelmingly in the third trimester | Maternal | This is why a preterm infant is more susceptible to infection: they were delivered before the bulk of the transfer occurred. Maternal IgG has a half-life of about 3–4 weeks, producing a physiologic nadir at 3 to 6 months as maternal antibody wanes before the infant's own production matures |
| IgM | NO — the molecule is too large | Fetal/neonatal production only | Elevated IgM in cord or neonatal blood means the fetus mounted its own antibody response in utero — a congenital infection. IgM is also the first antibody produced in any acute infection |
| IgA | NO | Secretory IgA is delivered by colostrum and breast milk | Coats the gastrointestinal and respiratory mucosa and blocks pathogen adherence. This is one of the strongest arguments for early colostrum, including oral immune therapy for infants who cannot yet feed |
Other immune deficits of the newborn
- Reduced neutrophil storage pool. The neonate can exhaust its marrow reserve rapidly, which is why neutropenia in a septic neonate is more ominous than neutrophilia — it means the reserve is spent.
- Immature complement and poor opsonization, impairing killing of encapsulated organisms.
- Skin and mucosal barriers are thin and easily breached, and every indwelling line is a highway past them.
Interpreting the laboratory work
| Test | Interpretation |
|---|---|
| White blood cell count with differential | Both leukocytosis and leukopenia occur; absolute neutrophil count interpreted against age-specific reference curves is more useful than the total WBC. Values shift dramatically in the first 12–24 hours, so a CBC drawn at 4 hours has a different reference range than one drawn at birth |
| Immature-to-total (I:T) neutrophil ratio | ≥ 0.2 suggests a left shift consistent with bacterial infection. It has a good negative predictive value but a poor positive predictive value — a normal I:T is more informative than an abnormal one |
| C-reactive protein (CRP) | An acute-phase reactant that begins rising 6 to 12 hours after the onset of inflammation and peaks at 24–48 hours. A single CRP drawn at the moment of the sepsis evaluation is often normal and must not be used to withhold antibiotics. Two normal serial CRPs at approximately 24 and 48 hours have a high negative predictive value and are widely used to stop antibiotics |
| Procalcitonin | Rises faster than CRP but has a physiologic postnatal surge in the first 48 hours that must be accounted for |
Bottom line for the bedside nurse: blood culture is the diagnostic standard; the acute-phase reactants are for de-escalation, not for deciding whether a symptomatic infant needs antibiotics now.
2. Congenital Infections (TORCH)
| Infection | Classic Neonatal Findings | The Discriminating Feature | Management |
|---|---|---|---|
| Cytomegalovirus (CMV) | The most common congenital infection. Microcephaly, periventricular intracranial calcifications, petechiae/"blueberry muffin" spots, hepatosplenomegaly, jaundice, chorioretinitis, IUGR | The leading non-genetic cause of sensorineural hearing loss. Most infected infants are asymptomatic at birth yet can still develop progressive hearing loss — which is why hearing screening and follow-up matter so much | Diagnose by urine or saliva PCR obtained within the first 21 days of life (later sampling cannot distinguish congenital from postnatally acquired infection). Symptomatic infants may receive valganciclovir; lifelong audiologic follow-up |
| Toxoplasmosis | Classic triad: chorioretinitis, hydrocephalus, and DIFFUSE (scattered) intracranial calcifications | Calcification pattern is the discriminator — diffuse in toxoplasmosis, periventricular in CMV | Pyrimethamine, sulfadiazine, and leucovorin. Prevention: avoid undercooked meat and cat litter in pregnancy |
| Rubella | Cataracts, sensorineural deafness, patent ductus arteriosus and peripheral pulmonic stenosis, "blueberry muffin" rash, radiolucent bone disease, microcephaly | The cardiac lesions plus cataracts | Supportive. Infants shed virus for months and require contact isolation; keep non-immune and pregnant staff away |
| Congenital syphilis | "Snuffles" (copious, persistent, infectious nasal discharge), a maculopapular rash involving the palms and soles, hepatosplenomegaly, osteochondritis and periostitis producing pseudoparalysis of Parrot, hydrops | Rash on palms and soles plus snuffles | Penicillin G — the only adequate treatment. Nasal secretions and moist lesions are highly infectious: gloves for all contact until 24 hours of therapy |
| Varicella | Congenital varicella syndrome (maternal infection in the first two trimesters): cicatricial scarring in a dermatomal pattern, limb hypoplasia, eye and CNS anomalies. Perinatal varicella (maternal rash from 5 days before to 2 days after delivery) is a severe, potentially fatal disseminated illness | The timing of the maternal rash determines which syndrome | Perinatal exposure requires varicella-zoster immune globulin (VariZIG) and isolation |
| Parvovirus B19 | Fetal aplastic crisis, severe anemia, non-immune hydrops fetalis | Anemia without hemolysis markers | Intrauterine transfusion; postnatal transfusion as needed |
| Herpes simplex virus | Three patterns: skin-eye-mouth; CNS disease (seizures, lethargy, often in the second week); and disseminated disease (shock, hepatitis, coagulopathy) | Most transmission comes from mothers with no history of genital herpes | Surface, blood, and CSF PCR plus liver enzymes; empiric IV acyclovir immediately while results pend |
3. Perinatally Transmitted Bloodborne Infections
Hepatitis B
- Mother HBsAg-positive: give hepatitis B vaccine AND hepatitis B immune globulin (HBIG) within 12 hours of birth, at two separate sites, regardless of birth weight. For infants under 2,000 g, the birth dose does not count toward the series and three further doses are required.
- Mother HBsAg-negative: give the hepatitis B vaccine birth dose within 24 hours for medically stable infants weighing ≥ 2,000 g.
- Mother's status unknown: give the vaccine within 12 hours and test the mother urgently; add HBIG if she proves positive (within 7 days for term infants, immediately for infants < 2,000 g).
- Breastfeeding is not contraindicated once immunoprophylaxis has been given.
HIV
- Maternal antiretroviral therapy with viral suppression reduces transmission to well under 1%.
- The infant receives antiretroviral prophylaxis (zidovudine, or a combination regimen when maternal viral load is not suppressed), started as soon as possible after birth.
- Diagnosis uses virologic testing (HIV DNA/RNA PCR), never antibody testing, because maternal IgG antibody crosses the placenta and will produce a positive antibody test in an uninfected infant for up to 18 months. Testing occurs at approximately 14–21 days, 1–2 months, and 4–6 months.
- In the United States, breastfeeding is not recommended when the mother is HIV-positive, and formula is provided; guidance elsewhere differs where safe replacement feeding is not available.
- Bathe the infant before any injection or heel stick to remove maternal blood and secretions.
4. Sexually Transmitted Infections Affecting the Eye and Airway
Gonococcal ophthalmia neonatorum
- Onset day 2 to 5. Hyperacute, profuse purulent conjunctival discharge with marked lid edema.
- This is an ocular emergency — Neisseria gonorrhoeae penetrates intact corneal epithelium and can cause corneal ulceration and globe perforation within days.
- Treatment: a single dose of ceftriaxone IM (substitute cefotaxime when the infant is hyperbilirubinemic, because ceftriaxone displaces bilirubin from albumin), plus saline eye irrigation. Evaluate for disseminated disease.
Chlamydial infection
- Conjunctivitis, onset day 5 to 14 — later than gonococcal, and initially watery before becoming mucopurulent.
- Chlamydial pneumonia at 4 to 12 weeks: an afebrile infant with a distinctive staccato cough, tachypnea, hyperinflation on radiograph, and eosinophilia.
- Treatment is systemic: oral erythromycin or azithromycin. Topical therapy does not eradicate nasopharyngeal carriage and does not prevent pneumonia. Counsel parents that erythromycin in young infants carries an association with infantile hypertrophic pyloric stenosis — teach them to report projectile vomiting.
The prophylaxis gap you must know
Erythromycin 0.5% ophthalmic ointment prevents gonococcal ophthalmia but does NOT prevent chlamydial conjunctivitis. An infant who received routine eye prophylaxis and returns on day 8 with conjunctivitis has not been protected against chlamydia, and a diagnosis of chlamydial conjunctivitis in an infant mandates treatment of the mother and her partner(s).
Human papillomavirus (HPV)
Vertical transmission can seed the larynx, producing juvenile-onset recurrent respiratory papillomatosis. It does not present in the nursery: the infant returns months to years later with progressive hoarseness, a weak or abnormal cry, and stridor. Cesarean delivery does not reliably prevent transmission and is not performed for this indication alone.
5. Enteroviral and Fungal Infection
- Enterovirus (including coxsackievirus and echovirus): peaks in summer and autumn. Presents as a sepsis-like illness in the first two weeks with fever, irritability, poor feeding, and rash, and can progress to myocarditis, fulminant hepatitis with coagulopathy, and meningoencephalitis. CSF pleocytosis with negative bacterial cultures should prompt enteroviral PCR. Management is supportive.
- Candida: congenital cutaneous candidiasis presents at or within hours of birth as a diffuse maculopapular or pustular rash including the palms and soles. Late-onset invasive candidiasis is a disease of very low birth weight infants with central lines, prolonged broad-spectrum antibiotics, and prolonged parenteral nutrition — and it is a powerful argument for antimicrobial stewardship and early enteral feeding.
6. Infection Control on the Unit
- Hand hygiene is the single most effective intervention in neonatal infection control — more effective than any antibiotic, isolation policy, or product. Alcohol-based rub for routine care; soap and water when hands are visibly soiled or after caring for an infant with C. difficile.
- Standard precautions apply to every infant, every time, because most infectious infants are not yet identified.
- Add contact precautions for rubella (prolonged shedding), congenital syphilis until 24 hours of penicillin, RSV and other respiratory viruses; airborne plus contact for varicella and disseminated zoster.
- Visitation: restrict symptomatic visitors and siblings during respiratory virus season, verify visitor immunization status, and require hand hygiene at every entry. These are not hospitality rules — they are the outer perimeter of the infection-control program.
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Test Your Knowledge
A term infant is evaluated for microcephaly, petechiae, and hepatosplenomegaly. Cranial imaging shows periventricular intracranial calcifications. Cord blood shows an elevated IgM level. Which infection is most consistent with these findings, and what diagnostic specimen timing is critical?
A
B
C
D
Test Your Knowledge
An 8-day-old infant who received erythromycin ophthalmic ointment at birth presents with mucopurulent discharge and swelling of both eyes. Conjunctival testing confirms Chlamydia trachomatis. Which statement should guide the nurse's teaching and plan of care?
A
B
C
D
Test Your Knowledge
A 6-hour-old infant with maternal chorioamnionitis has temperature instability and poor feeding. The initial C-reactive protein is 0.4 mg/dL (normal). The blood culture is pending. What is the most appropriate interpretation of the normal CRP?
A
B
C
D