Current guidelines recommending hospital observation for at least 5 to 10 days after the last episode of apnea in otherwise healthy premature infants appears to be supported by clinical investigation. Apnea is the spontaneous cessation of breathing often observed in premature babies. The medical charts of 91 pre-term infants with recurrent apnea were analyzed to determine the maximum interval between the last three apneas experienced before discharge. In babies with no other risk factors for apnea, those who had not had an occurrence for 8 days or more were unlikely to have another., ABSTRACT. Objective. Most neonatologists include an apnea-free period in the criteria for the discharge of preterm infants. However, the length of time one should wait after the cessation of apnea before sending an infant home without a monitor is debated. We undertook this study in an attempt to define a minimal and safe observation period between the time of the last apnea episode and discharge. Methods. We reasoned that in infants with idiopathic apnea of prematurity, the intervals between days on which apnea occurs gradually increase until some point at which clinically significant apnea ceases. Therefore, knowledge about the intervals between days on which apnea occurred just before the last apnea would provide a reasonable estimate of the minimal safe observation interval between the last apnea and discharge. We reviewed the charts of 266 infants born in 1993 and 1994 at [is less than or equal to] 32 weeks' gestational age or weighing [is less than or equal to] 51500 g at birth from two institutions to determine the intervals between the day on which the last apnea occurred and the previous two days on which apnea occurred. One hundred seventy-five infants were excluded because they never experienced apnea, or data about the last apnea was missing, or they were on xanthines during the period encompassing the last 3 apnea days, or they weighed < 1500 g or were < 34 weeks' postmenstrual age at the time of the last apnea. Of the 91 remaining infants, gestational age at birth, birth weight, 1- and 5-minute Apgar scores, and discharge weight were not different between the two institutions. For each infant we determined the longest of the intervals between the 2 days on which apnea occurred previous to the day of the last apnea (MAXINT for maximum interval). The infants were then ordered by MAXINT and, starting at the longest MAXINT, the medical records of each infant were carefully examined for other conditions known to be associated with apnea (eg, recovering from anesthesia, sepsis, chronic lung disease, and so forth). The minimal safe observation period was then defined as the longest MAXINT in which there was at least 1 infant with no other explanation for the apnea other than prematurity. Results. The median duration of the intervals between the 2 days on which apnea occurred previous to the day on which the last apnea occurred were 3.0 and 2.0 days and the median duration of the MAXINT was 4.0 days. On careful examination of the charts, it was determined that each of 13 infants with a MAXINT preceding the day on which the last apnea occurred of greater than 8 days had some other condition that might result in apnea, including residual lung disease, sepsis, surgery, and so forth. In contrast, among the group of infants with a MAXINT of [is less than or equal to]8 days, at least 1 infant at each MAXINT (eg, 1 to 8) had significant apnea with no other explanation other than prematurity. Conclusions. We conclude that otherwise healthy preterm infants continue to have apneas separated by as many as 8 days before the last apnea before discharge. Conversely, infants with longer apnea intervals often have identifiable risk factors other than apnea of prematurity. Pediatrics 1997;100:795-801; apnea of prematurity, premature newborn infant, hospital discharge criteria., ABBREVIATIONS. UVA, University of Virginia; DHMC, Dart-mouth-Hitchcock Medical Center; PMA, postmenstrual age; MAX-INT, maximum interval; ANOVA, analysis of variance; NICU, neo-natal intensive care unit; CPAP, continous positive pressure. A large [...]