Objective: A retrospective study was undertaken to determine if premature infants had a higher incidence of intrauterine growth retardation than term infants did. If premature labor is significantly associated with intrauterine growth retardation, then defining intrauterine growth retardation with a population-specific postnatal birth weight for gestational age curve would underestimate the incidence in preterm infants.
Study design: Data for the year 1990 were used to construct a postnatal birth weight for gestational-age curve. This curve was then used to analyze 1991 birth weight data and to determine the incidence of intrauterine growth retardation (< 10th percentile) at each week of gestation. Infants were also classified as having intrauterine growth retardation on the basis of an additional postnatal birth weight for gestational-age curve and two antenatal ultrasonic estimated fetal-weight-for-gestational-age curves.
Results: Analysis of the 1991 delivery data indicated that both ultrasonography curves showed a significant decrease in the incidence of intrauterine growth retardation with advancing gestational age, whereas the postnatal curves did not.
Conclusion: The results give full support to previous reports that suggest intrauterine growth retardation is more common in preterm than in term infants and are consistent with the hypothesis that intrauterine growth retardation is significantly related to premature birth.