BACKGROUND. Late-preterm infants are known to have greater morbidity and costs compared with term infants during the neonatal period, but less is known about whether these differences continue beyond this period.
OBJECTIVE. The purpose of this study was to examine the most common causes and costs of rehospitalization and other health care use among late-preterm and term infants throughout the first year of life.
METHODS. We conducted a retrospective cohort study of late-preterm (33–36 weeks' gestation) and term infants born in 2004 with ≥1 year of enrollment in a large national US database of commercially insured members. All of the reported health care services and costs were examined from the birth hospitalization through the first year of life.
RESULTS. We evaluated 1683 late-preterm and 33 745 term infants. The average length of stay of the birth hospitalization for term infants was 2.2 days, and the average cost was $2061. Late-preterm infants had a substantially longer average stay of 8.8 days and average cost of $26 054. Total first-year costs after birth discharge were, on average, 3 times as high among late-preterm infants ($12 247) compared with term infants ($4069). Late-preterm infants were rehospitalized more often than term infants (15.2% vs 7.9%). A subset of late-preterm infants that were discharged late from their birth hospitalization had the highest rates of rehospitalization and total health care costs. Higher costs during rehospitalization of late-preterm infants, especially those with a late discharge, indicate their propensity to have more severe illness.
CONCLUSIONS. Late-preterm infants have greater morbidity and total health care costs than term infants, and these differences persist throughout the first year of life. Management strategies and guidelines to reduce morbidity and costs in late-preterm infants should be investigated.
The overall rate of preterm birth in the United States increased 21.0% between 1990 and 2006 (10.6%–12.8%).1 The greatest increase occurred among late-preterm births or infants born at 34 to 36 weeks' gestation, which account for ∼75% of all preterm births.1,2 Although the increase in late-preterm births is believed to be attributable in part to an increase in multiple births, the rate of late-preterm singleton births has also been on the rise.1,3
Several studies indicate that late-preterm infants have greater morbidity and mortality perinatally than term infants.4–12 Tomashek et al6 and Kramer et al7 showed that late-preterm infants have a mortality rate 3 times greater than term infants, with the highest risk occurring during the neonatal period. Wang et al8 found significant differences in clinical outcomes during the birth hospitalization, such as temperature instability, hypoglycemia, respiratory distress, and jaundice, between late-preterm and term infants. Additional studies have shown an increased risk of rehospitalization among late-preterm compared with term infants during the neonatal period for conditions such as hyperbilirubinemia and feeding difficulties.9–11 Even studies that compared a subgroup of “healthy” late-preterm infants, defined as those discharged early (≤3 days) after birth, found rates of readmission during the neonatal period were still 2 to 3 times higher than term infants.9,11 Escobar et al12 found higher rates of rehospitalization between 15 and 185 days of life among late-preterm compared with term infants. Several studies examined the economic burden of preterm birth13–16; however, these focused on the cost differences between late-preterm and term infants during the birth hospitalization.
Information on the health consequences and costs beyond the birth hospitalization for late-preterm infants is limited. A recent report from the Institute of Medicine on the causes and consequences of preterm birth concluded that additional research on the economic, acute, and long-term outcomes for these vulnerable preterm infants is needed.17
This study, therefore, aimed to examine the health care burden imposed by late-preterm infants relative to term infants throughout the first year of life. Understanding the major causes of morbidity and costs may help physicians inform parents and optimize management for late-preterm infants. Furthermore, information on costs among these groups could assist formal evaluation of the cost-effectiveness of specific interventions.
We conducted a retrospective cohort study from a large US database of commercially insured members. Infants born in 2004 with ≥1 year of continuous enrollment were identified in the MedStat MarketScan Commercial Claims and Encounters database.18 The MedStat MarketScan Commercial Claims and Encounters database contains person-level enrollment and medical claims from ∼45 large employers, health plans, and government and public organizations, which represent an insured population of ∼17 million individuals and their dependents. Health care use and expenditures were available for inpatient, outpatient, prescription drug, and home health care services.
Study subjects were identified from newborn diagnosis-related group (DRG) codes (385–391) on the birth admission claim. Late-preterm infants were identified when their birth admission included either a DRG code for prematurity (386–388) or a DRG code during birth admission for neonate (385 and 390) and a diagnosis code for gestational age 33 to 36 weeks (International Classification of Diseases, Ninth Revision, Clinical Modification [ICD-9-CM] 765.27–8) reported on any claim during the first year of life. Term infants were identified by either a DRG code for term birth (389 and 391) or a combination of DRG (390) and diagnosis code for gestational age ≥37 weeks (ICD-9-CM 765.29). To avoid cases in which data submission may have been incomplete, infants were excluded if they were not associated with an employer group that contributed prescription drug claims data to the MarketScan databases or if they had a capitated insurance plan. Infants from a multiple birth (twin, triplet, etc) were identified with diagnosis codes (ICD-9-CM 761.5, V27.2–V27.7, or V31–V37). We excluded infants from multiple births if they did not have distinct enrollment identification numbers.
Claims associated with the infant's hospitalization at birth, including any transfers that may have occurred, were combined to calculate more accurately the length of stay and cost. The costs associated with the birth hospitalization included all of the professional and facility services, including physician fees, medications administered, and procedures performed. Maternal costs 30 days before the infant's birth, but excluding the day of birth and beyond, were assessed to understand additional resources that may have been associated with preterm birth.
Late-preterm infants were further classified as having either early or late discharge after birth. Consistent with previous research,11 early discharge was defined as <4 days from the date of birth, and late discharge was defined as a discharge ≥4 days from the date of birth.
Rehospitalizations were defined as hospital admissions occurring during the first year of life but after discharge from the birth hospitalization. Similar to Escobar et al,12,19 rehospitalizations within the short-term period were defined as those occurring within 15 days after the birth discharge date. Rehospitalizations within the long-term period were defined as those occurring on the 15th or subsequent day after the date of discharge after birth until the infant's first birthday.
The costs reported in this study were measured by using the allowed amount reported on the medical claim. The allowed amount reflects the negotiated reimbursement level for an approved service and represents the total compensation that the provider expected to receive for the services rendered. The database underlying this analysis reflected multiple payers and benefit designs across most states in the United States. The reimbursement levels associated with the services reflected characteristics associated with the payer, the provider, and the patient. The claims data were not adjusted to address outlier payment levels, including either high or low dollar amounts or long or short lengths of stay.
Descriptive statistics were presented as proportions for resource use and mean, median, and 95% confidence intervals for costs. All of the analyses were conducted by using SAS 9.1 (SAS Institute, Inc, Cary, NC).
Of the 75 640 infants born in 2004, 37 970 met the inclusion and exclusion criteria, including having ≥1 complete year of follow-up information available. Among these infants, 4225 (11.1%) were born preterm, and the remainder, 33 745 (88.9%), were born at term. For those born preterm, 2300 (54.4%) had a diagnosis code identifying gestational age at birth, of whom 1683 (73.2%) were coded as 33 to 36 weeks' gestation and constituted the late-preterm group. Maternal claims were available for 84.0% of all of the late-preterm and term infants.
Demographic comparisons of late-preterm and term infants revealed that a higher proportion of late-preterm infants were boys (55.3% vs 50.4%; P < .0001), had low birth weight (50.1% vs 0.5%; P < .0001), were from a multiple birth (26.0% vs 1.2%; P < .0001) and had preferred provider organization insurance (61.8% vs 54.6%; P < .0001) compared with term infants. The majority (66.0%) of late-preterm infants had a late discharge (≥4 days) after their birth hospitalization. Compared with late-preterm infants with an early discharge (<4 days) after their birth, infants who were discharged late were more likely to have had low birth weight (61.3% vs 21.4%; P < .0001), have been from a multiple birth (30.1% vs 17.9%; P < .0001), and to have had managed care (23.4% vs 16.8%; P = .002) or unmanaged insurance plans (13.5% vs 10.2%; P = .052).
The average length of stay of the birth hospitalization for term infants was 2.2 days and the average cost was $2087, whereas late-preterm infants had a substantially longer average stay of 8.8 days and cost of $26 054 (Table 1). The late-preterm infants with late discharge had mean and median costs from birth hospitalization that were 18 times higher than those of term infants. Late-preterm infants who were discharged early had the same length of stay during their birth hospitalization as term infants, but on average their associated costs were 2.5 times greater. This trend was consistent for both singletons and infants from multiple births. Term infants from multiple births had an average length of stay of 3.4 days and an average cost of $4035, whereas late-preterm infants from multiple births who were discharged early had an average length of stay of 2.4 days and an average cost of $7062.
Average maternal costs were also higher among late-preterm infants ($6672) compared with term infants ($1943; Table 1). However, among the late-preterm infants, those with early discharge had the greatest maternal costs, ∼4 times higher than term infants, whereas the maternal costs for late-preterm infants with later discharge were twice those of term infants.
The total first-year costs after birth discharge, on average, were also markedly higher among late-preterm infants ($12 247) compared with term infants ($4069; Table 1). Late-preterm infants had higher costs across every type of service category compared with term infants (Fig 1). For late-preterm infants, the most common contributors to costs, in rank order, were (1) inpatient hospitalizations, (2) well-infant physician office visits, and (3) outpatient hospital services. In contrast, the most common causes of costs for term infants were (1) well-infant physician office visits, (2) inpatient hospitalization, and (3) outpatient hospital services. Other notable differences between term and late-preterm infants were seen for home health care services and prescription drug use. Infants from multiple births had slightly higher first-year costs ($5356 for term and $16 518 for late-preterm infants) compared with singletons ($4053 for term and $10 749 for late-preterm infants).
Late-preterm infants, whether discharged early or late after birth, were almost twice as likely as term infants to have been rehospitalized at some time during their first year of life (Table 2). This trend was consistent for singletons (7.9% of term and 15.7% of late-preterm infants), but the difference for infants from multiple births was less remarkable (8.8% of term and 13.7% of late-preterm infants). Among infants who were rehospitalized, late-preterm infants, on average, and especially those with late discharge, had a greater number of hospitalizations and higher costs than term infants.
A significantly greater proportion of late-preterm infants (3.8%) were rehospitalized during the short-term, within 2 weeks of discharge after birth, compared with term infants (1.3%; P < .0001; Table 2). A greater proportion of the late-preterm infants who were discharged late required rehospitalizations over the long-term (13.1%) than did those discharged early (10.0%; P = .064). However, late-preterm infants with early discharge had a higher rate of rehospitalization during the short-term period (5.3% vs 3.1%; P = .027) compared with those with late discharge.
During the short-term period, jaundice was the most common cause of rehospitalization among late-preterm infants with early discharge and among term infants but was less common among late-preterm infants discharged late (Table 3). During the long-term period, respiratory and digestive disorders accounted for ∼50% of all of the rehospitalizations among each of the groups of infants (Fig 2). Bronchiolitis because of respiratory syncytial virus was the leading cause of rehospitalization during the long-term period among both late-preterm and term infants (Table 4).
Late-preterm infants have substantially higher costs than term infants, and the magnitude of this economic burden maybe greater than recognized previously. Although the birth hospitalization contributed a large proportion of total costs, late-preterm infants continued to use more health care resources throughout the first year of life compared with term infants. In every health care service group, late-preterm infants cost more than term infants. In addition, major differences in costs occurred with services indicative of more serious health conditions, namely, rehospitalizations, outpatient hospital visits, and home health care services.
This study, in contrast to most previous studies, included infants who were from multiple births. When late-preterm infants from multiple births were compared with singletons, infants from multiple births did not have higher rates of rehospitalization but did have higher costs during the first year after discharge from birth. This finding was also observed among term infants. Because infants of multiple births are recognized as being at increased risk for long-term health problems,20 this may be 1 subgroup that is closely followed after birth, thereby explaining the trend of having higher annual costs.
Another important finding of this study is that the majority of late-preterm infants had a delayed discharge after birth. Previous studies concerning late-preterm infants primarily examined the risk of rehospitalization among “healthy” or late-preterm infants with early discharge; however, according to our study, two thirds of late-preterm infants have a late discharge. To estimate more accurately the burden imposed by preterm infants, this subgroup needs to be examined further. The late-preterm infants who were discharged later had higher costs than those with early discharge, indicating that the former are a subset at particular risk of needing subsequent care. These infants may be identified at birth by their late discharge, which would allow plans for their subsequent care to be in place before they are discharged. However, late-preterm infants discharged early, who may be viewed as healthy, also used significantly more medical resources during their birth hospitalization and had higher rates of rehospitalization in their first year than term infants.
Higher rates of rehospitalization among late-preterm infants occurred within 15 days of discharge and continued throughout the first year of life. Furthermore, those with late discharge had the highest risk of rehospitalization during the long-term period, the greatest number of rehospitalizations per infant, and the highest average cost of rehospitalization. Respiratory and digestive disorders were the 2 most common conditions affecting all of the subgroups of infants. Previous studies have documented that respiratory syncytial virus is the leading cause of hospitalization among all infants nationwide.21 Our study revealed that this was also true for late-preterm and for term infants when examined separately. Overall, rehospitalization costs for most illnesses were higher for late-preterm infants than for term infants, suggesting that late-preterm infants have a propensity for more severe illness and require more medical services when hospitalized.
Important limitations of this study exist. First, claims data for gestational age were available for only slightly more than half of the infants, thus potentially compromising the ability to generalize our results to all late-preterm infants. Second, our population was from a large cohort of commercially insured infants; thus, infants covered through the Medicaid or State Children's Health Insurance Programs were not included. Data from an employed population with insurance coverage may not be generalizable to those with limited access to quality health care. Third, the claims-based approach did not allow access to important clinical information, such as socioeconomic status, breastfeeding, and ethnicity. Fourth, because gestational age ICD-9-CM codes combine infants born at 33 and 34 weeks' gestation, we were unable to separate the specific group of infants who meet the recommended definition of late-preterm (34–36 weeks' gestation) infants.4 Finally, this study also included infants who survived their first year of life, and because prematurity is associated with higher infant mortality, we may have underestimated the magnitude of the differences between the costs of late-preterm and term infants.
Late-preterm infants had substantially higher morbidity and costs during the hospitalization at birth, and these differences persisted throughout the first year of life. Late-preterm infants seem to be particularly vulnerable to respiratory and gastrointestinal illnesses throughout their first year of life.4 Yet, the significant economic burden that these illnesses cause among this group of preterm infants is not generally appreciated. The higher costs during rehospitalization of late-preterm infants, especially those with a late discharge, indicate their propensity to have more severe illness. Future studies are needed to investigate strategies for managing these infants that can reduce their morbidity and the associated costs. Our findings support and emphasize the Institute of Medicine recommendations for the development of guidelines tailored to the specific needs of late-preterm infants.17
This study was funded by MedImmune.
- Accepted June 4, 2008.
- Address correspondence to Kimmie K. McLaurin, MS, MedImmune, One MedImmune Way, Gaithersburg, MD 20878. E-mail:
Financial Disclosure: Ms McLaurin and Dr Mahadevia are employees of MedImmune; Dr Hall, Ms Jackson, and Ms Owens are paid consultants for MedImmune.
What's Known on This Subject
A recent report from the Institute of Medicine on the causes and consequences of preterm birth concluded that additional research on the economic, acute, and long-term outcomes for late-preterm infants is needed.
What This Study Adds
In this study we examined the health care burden imposed by late-preterm infants relative to term infants throughout the first year of life. Understanding the major causes of morbidity and costs may help physicians inform parents and optimize management for late-preterm infants.
- ↵Engle WA, Tomashek KM, Wallman C; American Academy of Pediatrics, Committee on Fetus and Newborn. “Late-preterm” infants: a population at risk [published correction appears in Pediatrics. 2008;121(2):451]. Pediatrics.2007;120 (6):1390– 1401
- Raju TN, Higgins RD, Stark AR, Leveno KJ. Optimizing care and outcome for late-preterm (near-term) gestations and for late-preterm infants: a summary of the workshop sponsored by the National Institutes of Health and Human Development. Pediatrics.2006;118 (3):1207– 1214
- ↵Wang ML, Dorer DJ, Fleming MP, Catlin EA. Clinical outcomes of near-term infants. Pediatrics.2004;114 (2):372– 376
- Escobar GJ, Greene JD, Hulac P, et al. Rehospitalisation after birth hospitalization: patterns among infants of all gestations. Arch Dis Child.2005;90 (2):125– 131
- Russell RB, Green NS, Steiner CA, et al. Cost of hospitalization for preterm and low birth weight infants in the United States. Pediatrics.2007;120 (1). Available at: www.pediatrics.org/cgi/content/full/120/1/e1
- Clements KM, Barfield WD, Ayadi MF, Wilber N. Preterm birth-associated cost of early intervention services: an analysis by gestational age. Pediatrics.2007;119 (4). Available at: www.pediatrics.org/cgi/content/full/119/4/e866
- ↵Schmitt SK, Sneed L, Phibbs, CS. Costs of newborn care in California: a population-based study. Pediatrics.2006;117 (1):154– 160
- ↵Institute of Medicine. Preterm Birth: Causes, Consequences, and Prevention. Washington, DC: National Academies Press; 2006
- ↵Medstat Group Inc. Marketscan Database. Ann Arbor, MI: Medstat Group Inc; 2004
- ↵Escobar GJ, Joffe SJ, Gardner MN, Armstrong MA, Folck BF, Carpenter DM. Rehospitalization in the first two weeks after discharge from the neonatal intensive care unit. Pediatrics.1999;104 (1). Available at: www.pediatrics.org/cgi/content/full/104/1/e2
- Copyright © 2009 by the American Academy of Pediatrics