Ballard Score Components
The Ballard Score (specifically the New Ballard Score) assesses gestational age through 12 distinct components divided into two categories: 6 neuromuscular maturity signs and 6 physical maturity signs, with each component scored individually and summed to estimate gestational age.
Neuromuscular Maturity Components (6 items)
The neuromuscular assessment evaluates active muscle tone and reflexes:
- Posture - Assessment of the degree of flexion in arms and legs at rest 1
- Square window - Flexibility of the wrist, measuring the angle between the palm and forearm 2
- Arm recoil - Speed and degree of recoil after passive extension of the arms 2
- Popliteal angle - Degree of extension possible at the knee joint 2
- Scarf sign - How far the elbow can be moved across the chest 1
- Heel to ear - Flexibility of hip joints when bringing the foot toward the ear 2
Physical Maturity Components (6 items)
The physical assessment evaluates external characteristics:
- Skin - Texture, thickness, and degree of peeling or cracking 3, 4
- Lanugo - Amount and distribution of fine body hair 2
- Plantar surface - Depth and extent of creases on the sole of the foot 3, 4
- Breast - Size of breast tissue bud and areola characteristics 2
- Eye/ear - Eyelid fusion and ear cartilage firmness 2
- Genitals - Development of external genitalia (male: testicular descent and scrotal rugae; female: labial development) 2
Scoring Methodology
- Each of the 12 components receives a score typically ranging from -1 to 5, depending on the degree of maturity observed 2
- The individual scores are summed to produce a total raw score 2
- The total score is then converted to an estimated gestational age using a standardized conversion table 2
- The neuromuscular components tend to be more reliable than physical components, particularly in certain populations 2
Critical Clinical Caveats
The Ballard Score has significant limitations that must be recognized:
- Extreme prematurity (<28 weeks): The score systematically overestimates gestational age by 1.3 to 3.3 weeks at each week from 22-28 weeks, with extremely wide confidence intervals (6.8 to 11.9 weeks) 5
- Small-for-gestational-age (SGA) neonates: Physical maturity scores overestimate gestational age by approximately 0.7 weeks, primarily due to accelerated maturation of skin and plantar creases 3
- Maternal corticosteroid exposure: Prenatal corticosteroid therapy causes the score to overestimate gestational age by 1.2-2.9 weeks 4
- Timing of assessment: The score is validated for use within the first 48-96 hours of life, though recent evidence suggests validity extends to day 7 with slight overestimation increasing with postnatal age 2
The score should never be used as the sole basis for critical decisions about initiating or withholding intensive care in extremely premature infants 5. First-trimester ultrasound with crown-rump length measurement remains the gold standard for gestational age determination, providing accuracy within ±5-7 days 6.