Postconceptional age of surviving preterm low-birth-weight infants at hospital discharge

Background: Prediction of the duration of hospital stay of preterm, low-birth-weight infants currently requires inconvenient referral to published tables. Objective: To determine whether postconceptional age (gestational age plus chronologic age) could serve as a useful clinical marker for the more convenient prediction of individual durations of hospital stay. Design: Case series. Setting: Regional military teaching medical center with level III obstetric and neonatal services. Patients: Nine hundred sixty surviving preterm, low-birth-weight infants in the neonatal intensive care unit. Main Outcome Measure: The strength of the relationship of birth weight to postconceptional age at the time of discharge was tested by analysis of variance. Results: Postconceptional age at the time of hospital discharge varied in a highly predictable manner with birth weight (P<.001). The mean and variance were greatest for infants with very low birth weights and decreased with increasing birth weight. Postconceptional age at the time of discharge reached a minimum of 36.0+/-1.4 weeks (mean+/-SD) for infants with birth weights of 1750 to 2240 g. Conclusions: Most preterm, ion-birth-weight infants meet current eligibility criteria for hospital discharge at a postconceptional age of 35 to 37 weeks. This level of maturity is sufficiently predictive to serve as a convenient, easy-to-remember clinical marker for expected durations of hospital stay. For infants with birth weights of less than 1000 g, discharge at a postconceptional age of 37 to 42 weeks is a more realistic expectation.