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, low-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.

(Arch Pediatr Adolesc Med. 1996;150:260-262)