Gestational age assessment and preterm classification — viva

Stem

Examiner-led viva on gestational age assessment and preterm classification. [3]

Examiner: How do you assign this infant's gestational age, given the mother is unsure of her dates? [3]

Strong answer: I anchor on the first-trimester crown-rump-length ultrasound, which dated the pregnancy at 31 weeks and 3 days and is the reference standard at about 5 to 7 days. Because the last menstrual period is uncertain, the ultrasound estimate stands as the single best estimate. [3]

Examiner: How would you confirm the age postnatally? [1]

Strong answer: I perform the New Ballard Score, six neuromuscular and six physical criteria, reliable to about plus or minus two weeks. It confirms the estimate in a well infant; in a sick or oedematous infant it is confirmatory only, with the ultrasound as the anchor. [1]

Examiner: The infant weighs 1900 g. Is this appropriate for gestational age? [2]

Strong answer: I classify size-for-gestational-age against the INTERGROWTH-21st newborn centiles, not against a fixed weight. At 31 weeks and 3 days, 1900 g is within the appropriate range, so this is an appropriate-for-gestational-age very preterm infant who is very low birthweight. [2]

Examiner: What screening does this gestational age trigger? [1] [7]

Strong answer: As a very preterm infant under 32 weeks and under 1500 g is not met here, but under 32 weeks alone triggers serial cranial ultrasound for intraventricular haemorrhage, and retinopathy of prematurity screening begins around 31 to 34 weeks postmenstrual age, driven by gestational age and birthweight. [1] [7]

Examiner: How do you follow this infant's growth and development? [7]

Strong answer: I plot on Fenton charts to 50 weeks postmenstrual age then transition to WHO or INTERGROWTH-21st standards, and I correct milestones for the weeks born early, continuing to about 2 years. Structured corrected-age follow-up runs to school age. [7]

Examiner: Name a classification trap you would guard against. [4] [5]

Strong answer: Two traps. Never conflate weight with age — a low weight at term is small-for-gestational-age, not prematurity. And never dismiss the late-preterm band (34 to 36 weeks and six days) as almost term, because it carries disproportionate morbidity and readmission risk. [5] [6] [4]