Perinatal infection screening and prevention — viva

Stem

The examiner hands you the antenatal and birth summary of a term infant: mother GBS-colonised, one dose of intrapartum penicillin given two hours before an otherwise normal vaginal delivery, membranes ruptured for 18 hours, no maternal fever. [1]

Examiner: What is your opening approach to this infant? [3]

Strong answer: I would first establish whether the infant is well or unwell, because that single judgement drives everything else. Intrapartum GBS prophylaxis was inadequate — fewer than four hours of antibiotics before delivery — so this infant is at increased risk of early-onset GBS sepsis. If the infant is well and term, I would perform a limited evaluation (blood culture and full blood count at 24 to 48 hours) and observe closely; if there is any sign of sepsis, I would move immediately to a full septic screen and empiric intravenous benzylpenicillin and gentamicin. [3]

Branch 1 — Screening framework

Examiner: Beyond GBS, what are the four universal antenatal screens and why? [3]

Strong answer: The four universal antenatal screens are HIV, hepatitis B, syphilis and rubella — each is common, transmissible and actionable, with a proven intervention. The framework for all perinatal infection prevention is a three-link chain: screen the mother, intervene around the time of birth, and protect and observe the newborn. A screen is only useful if it changes management — a positive GBS swab, for example, matters only once labour begins. [3]

Examiner probe: What is the difference between the United States and United Kingdom GBS policy? [4]

Strong answer: The United States, guided by the CDC revised 2010 guidelines (Verani) and endorsed by ACOG, recommends universal late-pregnancy GBS screening by vaginal-rectal swab. The United Kingdom, guided by RCOG Green-top Guideline 36, uses a risk-based approach and does not offer routine universal swabbing. The Cochrane review supports intrapartum antibiotics for known colonisation but the evidence for universal screening over a risk-based strategy is limited, which is why policies differ. [4]

Branch 2 — Hepatitis B and the birth dose

Examiner: The registrar asks why the hepatitis B birth dose matters when the mother is HBsAg negative. How do you respond? [9]

Strong answer: The birth dose of hepatitis B vaccine is recommended for every newborn because it closes a prevention gap — it protects infants whose mothers are HBsAg negative but who may be exposed perinatally or in early life, and it captures infants whose mother's status is unknown or was falsely recorded. For an HBsAg-positive mother, the infant receives the vaccine plus hepatitis B immunoglobulin within 12 hours, followed by completion of the series and post-vaccination serology. Forgetting the birth dose because a baby looks well is one of the classic preventable errors. [9]

Branch 3 — A trap

Examiner: A colleague says a normal full blood count at 12 hours excludes sepsis, so the infant can stay on the postnatal ward without observation. How do you respond? [3]

Strong answer: I would correct that. A single normal full blood count early in life does not exclude early-onset sepsis — a genuinely septic infant can have a normal early count. The decision to observe rather than treat is based on the infant being clinically well and on the trend of observations over hours, with a documented escalation plan. I would keep the at-risk infant under structured observation and treat immediately if any sign of sepsis appears. [3]