OBJECTIVES: To profile a cohort of women and infants who received a diagnosis of preterm labor (PTL)/preterm birth (PTB), and to compare the health care burden of these cohorts to term deliveries/infants. METHODS:   Retrospective analysis of Premier Perspective Hospital Database. Sample populations of women who delivered and infants who were born (2003-2010), were identified and a case controlled analysis was conducted comparing PTL-deliveries/PTB-infants with term deliveries/infants.  Secondary outcomes included summaries of resource utilization and costs.  Maternal cases and controls and infant cases and controls were matched 1 to 1, based on year of delivery/birth, mother’s delivery age (mothers only), race, provider area, rural/urban, and payor type. RESULTS:  A total of 432,808 women had a diagnosis code of PTL with delivery, the fewest (9.4%) in 2003 and the most (15.5%) in 2009.  Tocolytic drug use was recorded in 37% of cases. Cases with delivery had a mean length of stay (LOS) of 3.06 days (controls = 2.25 days) and mean per patient costs of $8032 (controls = $5311).    There were 314,577 case infants with either a gestational age (GA) ICD9 code or a birth weight ICD9 code.  Total mean cost per case with in-hospital deaths included was $70,074 (controls = $4,505). More deaths occurred in the case cohort versus the control cohort (6941 vs. 121, respectively). The case mean hospital LOS was 14.27 days (controls = 2.39 days).   The extremely premature (<25-26 wks) made up approximately 4% of PTBs and 22% of total hospital costs vs. late preterm (33-36 wks) made up approximately 69% of PTBs and 30% of total hospital costs. CONCLUSIONS:   The most extreme premature infants accounted for 22% of the total preterm hospital costs.  Being able to prolong the pregnancy across the entire GA range, but particularly in the very preterm, has the potential for substantial cost savings.