Exam
Genitals item to score
Show score choices as
Neuromuscular maturity
Examine the baby supine, quiet and warm. Crying or active resistance changes tone. The official chart shows a drawing for each score: open the illustrated score sheet.
Physical maturity
Result
Score to gestational age
Each 5 points is 2 weeks: estimated GA (weeks) = 24 + 0.4 × total score. Scores between rows are interpolated.
Accuracy and limits
Timing: best within the first 24–48 hours; usable to about 96 hours. Under 26 weeks, examine before 12 hours of life (97% within 2 weeks when done then). From 26 weeks on, agreement was stable (about 92%) up to 96 hours.
Accuracy: original validation (530 infants) r = 0.97, mean difference 0.15 ± 1.46 weeks. Independent pooled data are wider: tends to overestimate by about 0.4 weeks, 95% of differences within ±3.8 weeks of ultrasound dating, within 2 weeks in about 72%.
Extreme prematurity: before 28 weeks the score overestimated GA by 1.3–3.3 weeks, with very wide confidence intervals (NICHD Neonatal Research Network). Do not base viability or resuscitation decisions on it.
Growth restriction: may misestimate GA in very small-for-gestational-age infants.
Unreliable tone (sedation, maternal magnesium, opioids or anesthesia, asphyxia or HIE, illness, neuromuscular disease) distorts the neuromuscular items; the physical items are more trustworthy then.
With obstetric dating: don't revise a reliable first-trimester due date because of the Ballard score. Use it to estimate GA when dating is missing or unreliable, and to flag a difference of more than 2 weeks.