What are the indications and criteria for the Ballard evaluation in newborns?

Ballard Evaluation: Indications and Criteria

The Ballard evaluation (New Ballard Score) is indicated when gestational age needs to be determined or confirmed in newborns, particularly when obstetric dating is uncertain or unavailable, and should be performed ideally before 12 hours of age in extremely premature infants (<26 weeks) or within 96 hours for infants ≥26 weeks gestation. 1

Primary Indications for Ballard Assessment

The New Ballard Score (NBS) serves as a clinical tool for gestational age assessment in the following scenarios:

• Uncertain or unavailable obstetric dating - When last menstrual period (LMP) or prenatal ultrasonography data are unreliable or absent 1
• Confirmation of gestational age - To verify obstetric estimates, particularly in high-risk situations where accurate dating impacts clinical management 1
• Premature infants requiring intensive care decisions - Though accuracy limitations exist (discussed below), NBS may contribute to gestational age assessment in extremely premature neonates 2

Scoring Criteria and Components

The NBS evaluates 12 parameters total: 6 neuromuscular criteria and 6 physical maturity criteria 1

Neuromuscular Maturity Criteria:

• Posture
• Square window (wrist flexion)
• Arm recoil
• Popliteal angle
• Scarf sign
• Heel to ear maneuver

Physical Maturity Criteria:

• Skin texture and appearance
• Lanugo
• Plantar surface creases
• Breast tissue development
• Eye/ear formation
• Genitalia development

Each criterion receives a score, with the sum correlating to gestational age. The expanded NBS was specifically refined to include extremely premature infants from 20-44 weeks gestation 1

Optimal Timing of Assessment

Critical timing considerations differ by gestational age:

• Extremely premature infants (<26 weeks): Perform examination before 12 hours of postnatal age for greatest validity (97% agreement within 2 weeks of confirmed gestational age) 1
• Infants ≥26 weeks gestation: Examination remains valid throughout the first 96 hours of life, with consistent 92% agreement across all postnatal age categories 1
• General recommendation: Complete assessment within 48 hours of birth for optimal accuracy 3, 2

Accuracy and Reliability

The NBS demonstrates strong overall performance but with important limitations:

• Overall correlation: 0.97 correlation with confirmed gestational age by LMP and prenatal ultrasound 1
• Mean accuracy: Within 0.15 ± 1.46 weeks for the total population 1
• Interrater reliability: Excellent at 0.95 correlation between examiners 1

Critical Pitfalls and Limitations

Specific Populations with Reduced Accuracy:

Small-for-gestational-age (SGA) neonates: The physical maturity components, particularly skin texture and plantar creases, overestimate gestational age by approximately 0.7 weeks (mean difference) 4. The neuromuscular components remain accurate, but physical parameters show accelerated maturation in growth-restricted infants 4

Extremely premature infants (<28 weeks): NBS systematically overestimates gestational age by 1.3 to 3.3 weeks at each week from 22-28 weeks, with wide confidence intervals (6.8 to 11.9 weeks range) 2. This inaccuracy is clinically significant when making intensive care decisions 2

Infants exposed to prenatal corticosteroids: NBS tends to overestimate gestational age by 1.2 to 2.9 weeks compared to ultrasound/LMP dating, likely due to accelerated physical maturation from steroid exposure 3

Very low birth weight infants: Show increased discrepancies, with NBS overestimating gestational age 3

Clinical Implications:

• Do not use NBS as the sole determinant for decisions to initiate or withhold intensive care in extremely premature infants, given the significant inaccuracies 2
• Differences of more than 2 weeks between NBS and obstetric dating occur frequently enough to warrant caution 3
• In SGA infants, consider adjusting physical parameter scores (reducing skin and plantar crease scores from 4 to 3) to improve accuracy, which decreases overestimation to 0.4 weeks 4

Alternative or Complementary Assessments

When available, prenatal ultrasonography performed in the first or early second trimester remains the gold standard for gestational age determination and should take precedence over NBS 1

For very low birth weight infants, biometric measurements including foot length and intermamillary distance correlate significantly with gestational age and can complement clinical assessment 5