The primary purpose of this study was to evaluate the accuracy of gestational age (GA) estimates by using the New Ballard Score (NBS) in newborns 24 to 27 weeks GA with accurate obstetric estimates of GA. Secondary purposes were: (1) to compare the accuracy of GA estimates derived from the NBS, the original Ballard score, and the physical items of the original Ballard score and (2) to compare these measures of GA and best obstetric estimates of GA as predictors of survival, morbidity, and hospital stay among infants <28 weeks' gestation and among very low birth weight infants in general.

The Ballard maturational assessment is commonly used to estimate gestational age (GA) when the menstrual history and other obstetrical estimates of GA are uncertain. The original Ballard Score and the New Ballard Score are based on the assumption that the fetal skin, subcutaneous tissues, and neuromuscular system mature at predictable rates.

Because of variation in maturation rates among healthy fetuses or abnormalities of fetal development, fetal maturation can vary at a given GA. For very premature infants, small differences in GA result in large differences in outcome and may even determine whether intensive care is given.

The primary purpose of this study was to evaluate the accuracy of GA estimates by using the NBS in newborns 24 to 27 weeks GA with accurate obstetric estimates of GA. Secondary purposes were: (1) to compare the accuracy of GA estimates derived from the NBS, the original Ballard score, and the physical items of the original Ballard score and (2) to compare these measures of GA and best obstetric estimates of GA as predictors of survival, morbidity, and hospital stay among infants <28 weeks' gestation and among very low birth weight infants in general.

For this study, eligible infants included those with birth weights of 401-1500g born in the National Institute of Child and Human Development (NICHD) Neonatal Research Network (NRN). Before 48 hours of age, enrolled infants were examined using the New Ballard Score by trained and certified research nurses masked to obstetric estimates of gestational age. A best obstetrical estimate of GA, used for screening of potentially eligible infants, was determined from the last menstrual period, obstetrical measures, and ultrasound findings recorded on the labor and delivery records.

Inclusion Criteria:

• <28 weeks gestational age by best obstetrical estimate
• Availability of mother's prenatal records for review
• First prenatal visit occurred before 17 weeks' gestation
• Mother's menstrual history allowed calculation of GA at birth
• Mother reported the duration of her usual menstrual cycles as 21 to 35 days
• Mother had 3 consecutive normal menstrual cycles before the missed menstrual period identifying the index pregnancy
• Mother reported that she was certain within 4 days of the first day of the last menstrual period (as recorded at the time of the first prenatal visit)
• Mother denied use of birth control medication during the 3 months preceding the last menstrual period.

Exclusion Criteria:

• Inaccurate or unavailable menstrual histories

Infants born in the NICHD Neonatal Research Network during the study period.