Perinatal, Congenital, and Neonatal Infections
Core concepts
Perinatal infections are organized by timing. Early-onset neonatal sepsis (72 hours or less) reflects maternal genital flora: group B Streptococcus and Escherichia coli, with Listeria less common. Late-onset sepsis (7 days or more) adds coagulase-negative Staphylococcus and nosocomial organisms. Empiric therapy is ampicillin plus gentamicin; add cefotaxime when meningitis is suspected. Ceftriaxone is avoided in neonates because it displaces bilirubin and can precipitate with calcium. Congenital infections: CMV is the most common; also toxoplasmosis, syphilis, rubella, Zika, and HSV. Neonatal HSV can present without vesicles, so any febrile or ill neonate younger than 21-28 days deserves HSV evaluation and empiric acyclovir. Syphilis is treated with penicillin G; penicillin allergy in pregnancy requires desensitization.
Traps
- A negative maternal GBS screen does not exclude GBS disease.
- Cesarean delivery before labor with intact membranes does not require GBS prophylaxis.
- CSF PCR for HSV may be negative early; surface cultures and repeat CSF help.
- Neonatal HSV dosing is high-dose acyclovir, not the older 30 mg/kg/day regimen.
Worked example
A 5-day-old with temperature instability, poor feeding, and no focal findings: obtain blood culture, catheter urine culture, CSF cell count/culture/PCR, and surface HSV swabs; start ampicillin plus gentamicin, add cefotaxime for meningitis, and add acyclovir if HSV risk factors or illness is severe.
Rule of thumb: any neonate with fever or sepsis-like illness gets a full evaluation plus empiric coverage for GBS, E. coli, Listeria, and HSV when indicated.