Evaluation of perinatal outcome using individualized growth assessment: comparison with conventional methods.

OBJECTIVE: To evaluate individualized growth assessment using the Rossavik growth model for detection of growth-retarded neonates with poor perinatal outcomes.

METHODS: Rossavik growth models derived from second-trimester ultrasound measurements were used to predict birth characteristics of 154 singleton neonates. Individual fetal growth curve standards for head and abdominal circumference and weight were determined from the data of two scans obtained before 25 weeks' menstrual age and separated by an interval of at least 5 weeks. Comparisons between actual and predicted birth characteristics were expressed by the Growth Potential Realization Index and the Neonatal Growth Assessment Score (NGAS). The proportions of perinatal outcomes (mechanical delivery, low Apgar score, abnormal fetal heart rate [FHR] patterns, neonatal acidosis, meconium staining of amniotic fluid, neonatal intensive care unit admission, and maternal complications), using NGAS, were compared with those by the traditional birth weight-for-gestational age method and the ponderal index, respectively.

RESULTS: Of the 154 fetuses studied, 120 had normal growth outcomes at birth; 18 showed evidence of intrauterine growth retardation; and 16 had macrosomia, based on NGAS. According to birth weight-for-gestational age classification, 32 fetuses were small for gestational age; 118 were appropriate for gestational age; and only 4 were large for gestational age. According to the ponderal index, 55 fetuses had growth retardation, 99 showed appropriate growth and there was no macrosomia. There was a significant increase in mechanical deliveries in cases of growth-retarded neonates, determined using the NGAS classification, when compared with events related to normally grown or macrosomic neonates. However, there were no significant differences in mechanical deliveries among the groups by birth weight classification or ponderal index. Both birth weight classification and NGAS classification showed a significant increase in the low Apgar score, abnormal FHR patterns, and neonatal acidosis in infants classified as growth retarded when compared with appropriately grown or macrosomic infants. However, there were no significant differences in the low Apgar score, abnormal FHR patterns, and neonatal acidosis between growth-retarded and appropriately grown infants when they had been so classified by ponderal index. Three growth category classification methods failed to reveal significant differences in meconium staining of amniotic fluid, neonatal intensive care unit admission, and maternal complications among the groups.

CONCLUSION: We do cast doubt on the usefulness of the ponderal index for detection of growth-retarded neonates with poor perinatal outcomes, and individualized growth assessment seems to perform at least as well as the traditional birth weight-for-gestational age method.