Perinatal infection screening and prevention — formative SAQs

SAQ 1 (10)

A 38-week infant is born after 18 hours of ruptured membranes to a mother known to be colonised with Group B Streptococcus. She received one dose of intravenous benzylpenicillin two hours before delivery. At four hours of age the infant is grunting, tachypnoeic (respiratory rate 72) and has cool peripheries. [1] [3]

1. What is the most likely diagnosis and why is this infant at particular risk? (3) [3]
2. Outline your immediate investigations and management. (4) [3] [5]
3. How would your management differ if the infant were clinically well at four hours of age? (3) [3]

Model answer

1. The most likely diagnosis is probable early-onset Group B Streptococcal sepsis. The infant is at particular risk because maternal GBS colonisation was identified but intrapartum prophylaxis was inadequate — fewer than four hours of antibiotics before delivery — so fetal antibiotic levels were insufficient to reduce the inoculum at the time of birth-canal exposure. Grunting, tachypnoea and poor perfusion within the first 72 hours are the classic presentation. [1] [3]
2. Immediate management is a full septic screen — blood culture, full blood count and differential, lumbar puncture (cell count, protein, glucose, culture and HSV PCR if indicated), C-reactive protein, and chest radiograph — followed immediately by empiric intravenous benzylpenicillin and gentamicin to cover GBS and E. coli. Stabilise airway, breathing and circulation with oxygen and respiratory support, establish intravenous access, and treat poor perfusion with fluid and inotropes as needed; escalate to the neonatal team early. [3] [5]
3. If the infant were clinically well, the approach would be a limited evaluation — blood culture and full blood count at 24 to 48 hours — without routine lumbar puncture or empiric antibiotics, with close structured observation and a clear escalation plan. The decision to treat or observe is clinical, and the threshold to start treatment is low if the infant deteriorates. [3]

SAQ 2 (10)

A 28-year-old woman books late in pregnancy with no antenatal records. She is hepatitis B surface antigen positive on urgent testing and HIV status is unknown. [9]

1. What is the significance of her presenting with "no records", and what is your general principle in managing her infection risk? (2) [3] [9]
2. Outline the neonatal prophylaxis required for hepatitis B exposure. (4) [9]
3. Outline the framework for HIV prevention in this mother–infant pair. (4) [6] [7]

Model answer

1. "No records" means unknown risk, not low risk. The general principle is to treat hepatitis B and HIV status as untested (and to screen for syphilis), to protect the infant until results return, and to close the prevention chain — screen, intervene, protect and observe — rather than reassure on the absence of information. [3] [9]
2. The infant of an HBsAg-positive mother requires the hepatitis B vaccine plus hepatitis B immunoglobulin (HBIG) within 12 hours of birth, followed by completion of the vaccine series and post-vaccination serology to confirm protection rather than chronic carriage. This combination prevents the great majority of perinatal HBV transmission and the chronic carriage that would otherwise follow. [9]
3. HIV prevention is a package: urgent maternal testing, maternal combination antiretroviral therapy to suppress the viral load, consideration of the mode and timing of delivery, infant antiretroviral prophylaxis started as soon as possible after birth (regimen chosen with the HIV team on the basis of maternal viral load and resistance history), early virological testing of the infant by HIV PCR, and a safe, supported infant feeding plan. The legacy of PACTG 076 is that vertical transmission can be slashed, and modern combination therapy brings transmission below one to two percent. [6] [7]