A standardized method for assigning gestational age: a tool for measuring gestational age based newborn intensive care outcomes.

We developed a computer-generated algorithm for standardizing the assignment of a best gestational age. Our database collected information on maternal last menstrual period (LMP), prenatal ultrasonography, obstetrical estimated date of confinement (EDC), use of assisted reproductive technology (ART), and newborn assessment based on the Ballard examination. The algorithm for determining best gestational age was developed based on the literature on the accuracy of prenatal and neonatal dating. We examined the performance of the algorithm using patients admitted to our neonatal intensive care unit (NICU) with a best gestational age <or= 32 completed weeks. Based on agreement of the obstetric EDC with either the first-trimester ultrasonography or LMP and first- and second-trimester ultrasonography, 64.4% of patients were classified as having certain dating. The Ballard assessment played a role in assigning a best gestational age in 11.3% of patients. We demonstrated differences in outcomes based on dating certainty within subpopulations in our NICU. An objective standardized methodology for assigning gestational age is a useful tool for comparing gestational age-based outcome measures between institutions.