Ellen C. Hale

Neonatal Outcomes of Extremely Preterm Infants From the NICHD Neonatal Research Network

OBJECTIVE: This report presents data from the Eunice Kennedy Shriver National Institute of Child Health and Human Development Neonatal Research Network on care of and morbidity and mortality rates for very low birth weight infants, according to gestational age (GA). METHODS: Perinatal/neonatal data were collected for 9575 infants of extremely low GA (22–28 weeks) and very low birth weight (401–1500 g) who were born at network centers between January 1, 2003, and December 31, 2007. RESULTS: Rates of survival to discharge increased with increasing GA (6% at 22 weeks and 92% at 28 weeks); 1060 infants died at ≤12 hours, with most early deaths occurring at 22 and 23 weeks (85% and 43%, respectively). Rates of prenatal steroid use (13% and 53%, respectively), cesarean section (7% and 24%, respectively), and delivery room intubation (19% and 68%, respectively) increased markedly between 22 and 23 weeks. Infants at the lowest GAs were at greatest risk for morbidities. Overall, 93% had respiratory distress syndrome, 46% patent ductus arteriosus, 16% severe intraventricular hemorrhage, 11% necrotizing enterocolitis, and 36% late-onset sepsis. The new severity-based definition of bronchopulmonary dysplasia classified more infants as having bronchopulmonary dysplasia than did the traditional definition of supplemental oxygen use at 36 weeks (68%, compared with 42%). More than one-half of infants with extremely low GAs had undetermined retinopathy status at the time of discharge. Center differences in management and outcomes were identified. CONCLUSION: Although the majority of infants with GAs of ≥24 weeks survive, high rates of morbidity among survivors continue to be observed.

Early Onset Neonatal Sepsis: The Burden of Group B Streptococcal and E. coli Disease Continues

BACKGROUND: Guidelines for prevention of group B streptococcal (GBS) infection have successfully reduced early onset (EO) GBS disease. Study results suggest that Escherichia coli is an important EO pathogen. OBJECTIVE: To determine EO infection rates, pathogens, morbidity, and mortality in a national network of neonatal centers. METHODS: Infants with EO infection were identified by prospective surveillance at Eunice Kennedy Shriver National Institute of Child Health and Human Development Neonatal Network centers. Infection was defined by positive culture results for blood and cerebrospinal fluid obtained from infants aged ≤72 hours plus treatment with antibiotic therapy for ≥5 days. Mother and infant characteristics, treatments, and outcomes were studied. Numbers of cases and total live births (LBs) were used to calculate incidence. RESULTS: Among 396 586 LBs (2006–2009), 389 infants developed EO infection (0.98 cases per 1000 LBs). Infection rates increased with decreasing birth weight. GBS (43%, 0.41 per 1000 LBs) and E coli (29%, 0.28 per 1000 LBs) were most frequently isolated. Most infants with GBS were term (73%); 81% with E coli were preterm. Mothers of 67% of infected term and 58% of infected preterm infants were screened for GBS, and results were positive for 25% of those mothers. Only 76% of mothers with GBS colonization received intrapartum chemoprophylaxis. Although 77% of infected infants required intensive care, 20% of term infants were treated in the normal newborn nursery. Sixteen percent of infected infants died, most commonly with E coli infection (33%). CONCLUSION: In the era of intrapartum chemoprophylaxis to reduce GBS, rates of EO infection have declined but reflect a continued burden of disease. GBS remains the most frequent pathogen in term infants, and E coli the most significant pathogen in preterm infants. Missed opportunities for GBS prevention continue. Prevention of E coli sepsis, especially among preterm infants, remains a challenge.

Very low birth weight preterm infants with early onset neonatal sepsis: The predominance of Gram-negative infections continues in the National Institute of Child Health and Human Development Neonatal Research Network, 2002-2003

Background: Early onset neonatal sepsis (EOS, occurring in the first 72 hours of life) remains an important cause of illness and death among very low birth weight (VLBW) preterm infants. We previously reported a change in the distribution of pathogens associated with EOS from predominantly Gram-positive to primarily Gram-negative organisms. Objective: To compare rates of EOS and pathogens associated with infection among VLBW infants born at centers of the National Institute of Child Health and Human Development (NICHD) Neonatal Research Network during 3 time periods: 1991–1993; 1998–2000; and 2002–2003. Study Design: Prospectively collected data from the NICHD Neonatal Research Network VLBW registry were retrospectively reviewed. Rates of blood culture confirmed EOS, selected maternal and infant variables and pathogens associated with infection were compared between 2002–2003 and 2 previously published cohorts. Results: During the past 13 years, overall rates of EOS have remained stable (15–19 per 1000 live births of infants 401–1500 g). More than one-half of early infections in the 2002–2003 cohort were caused by Gram-negative organisms (53%), with Escherichia coli the most common organism (41%). Rates of group B streptococcal infections remain low (1.8 per 1000 live births). Between 1991–1993 and 1998–2000, there was a significant increase in rates of E. coli infections; but in 2002–2003, there was no significant change (7.0 per 1000 live births). Infants with EOS continue to be at significantly increased risk for death compared with uninfected infants. Conclusion: EOS remains an uncommon but important cause of morbidity and mortality among VLBW infants. Gram-negative organisms continue to be the predominant pathogens associated with EOS.

Causes and Timing of Death in Extremely Premature Infants from 2000 through 2011

BACKGROUND Understanding the causes and timing of death in extremely premature infants may guide research efforts and inform the counseling of families. METHODS We analyzed prospectively collected data on 6075 deaths among 22,248 live births, with gestational ages of 22 0/7 to 28 6/7 weeks, among infants born in study hospitals within the National Institute of Child Health and Human Development Neonatal Research Network. We compared overall and cause-specific in-hospital mortality across three periods from 2000 through 2011, with adjustment for baseline differences. RESULTS The number of deaths per 1000 live births was 275 (95% confidence interval [CI], 264 to 285) from 2000 through 2003 and 285 (95% CI, 275 to 295) from 2004 through 2007; the number decreased to 258 (95% CI, 248 to 268) in the 2008-2011 period (P=0.003 for the comparison across three periods). There were fewer pulmonary-related deaths attributed to the respiratory distress syndrome and bronchopulmonary dysplasia in 2008-2011 than in 2000-2003 and 2004-2007 (68 [95% CI, 63 to 74] vs. 83 [95% CI, 77 to 90] and 84 [95% CI, 78 to 90] per 1000 live births, respectively; P=0.002). Similarly, in 2008-2011, as compared with 2000-2003, there were decreases in deaths attributed to immaturity (P=0.05) and deaths complicated by infection (P=0.04) or central nervous system injury (P<0.001); however, there were increases in deaths attributed to necrotizing enterocolitis (30 [95% CI, 27 to 34] vs. 23 [95% CI, 20 to 27], P=0.03). Overall, 40.4% of deaths occurred within 12 hours after birth, and 17.3% occurred after 28 days. CONCLUSIONS We found that from 2000 through 2011, overall mortality declined among extremely premature infants. Deaths related to pulmonary causes, immaturity, infection, and central nervous system injury decreased, while necrotizing enterocolitis-related deaths increased. (Funded by the National Institutes of Health.).

Late-Onset Sepsis in Very Low Birth Weight Infants from Singleton and Multiple-Gestation Births

OBJECTIVES To describe and compare the incidence of late-onset sepsis (LOS) and demographic and clinical characteristics associated with LOS in very low birth weight (VLBW) infants from singleton and multiple births, and to examine the heritability of susceptibility to LOS among VLBW twins by comparing same-sex and unlike-sex twin pairs. STUDY DESIGN The study group comprised infants with birth weight 401-1500 g seen at clinical centers of the Eunice Kennedy Shriver National Institute of Child and Human Development Neonatal Research Network between 2002 and 2008. Only the first episode of LOS was included in our analysis. Stepwise logistic regression models were fitted separately for singleton and multiple pregnancies to examine the maternal and neonatal factors associated with LOS. LOS due solely to gram-negative bacteria in singleton and multiple pregnancies was also examined in separate models. The heritability of LOS was estimated by examining the concordance of LOS in twins from same-sex and unlike-sex pairs. RESULTS LOS occurred in 25.0% (3797 of 15,178) of singleton and 22.6% (1196 of 5294) of multiple-birth VLBW infants. Coagulase-negative staphylococci were the most common infecting organisms, accounting for 53.2% of all LOS episodes in singletons and 49.2% in multiples. Escherichia coli and Klebsiella species were the most commonly isolated gram-negative organisms, and Candida albicans was the most commonly isolated fungus. Concordance of LOS did not differ significantly between same-sex and unlike-sex twin pairs. CONCLUSION LOS remains a common problem in VLBW infants. The incidence of LOS is similar for singleton and multiple-birth infants. The similar concordance of LOS in same-sex and unlike-sex twin pairs provides no evidence that susceptibility to LOS among VLBW infants is genetically determined.

Chorioamnionitis and Culture-Confirmed, Early-Onset Neonatal Infections

BACKGROUND: Current guidelines for prevention of neonatal group B streptococcal disease recommend diagnostic evaluations and empirical antibiotic therapy for well-appearing, chorioamnionitis-exposed newborns. Some clinicians question these recommendations, citing the decline in early-onset group B streptococcal disease rates since widespread intrapartum antibiotic prophylaxis implementation and potential antibiotic risks. We aimed to determine whether chorioamnionitis-exposed newborns with culture-confirmed, early-onset infections can be asymptomatic at birth. METHODS: Multicenter, prospective surveillance for early-onset neonatal infections was conducted during 2006–2009. Early-onset infection was defined as isolation of a pathogen from blood or cerebrospinal fluid collected ≤72 hours after birth. Maternal chorioamnionitis was defined by clinical diagnosis in the medical record or by histologic diagnosis by placental pathology. Hospital records of newborns with early-onset infections born to mothers with chorioamnionitis were reviewed retrospectively to determine symptom onset. RESULTS: Early-onset infections were diagnosed in 389 of 396 586 live births, including 232 (60%) chorioamnionitis-exposed newborns. Records for 229 were reviewed; 29 (13%) had no documented symptoms within 6 hours of birth, including 21 (9%) who remained asymptomatic at 72 hours. Intrapartum antibiotic prophylaxis exposure did not differ significantly between asymptomatic and symptomatic infants (76% vs 69%; P = .52). Assuming complete guideline implementation, we estimated that 60 to 1400 newborns would receive diagnostic evaluations and antibiotics for each infected asymptomatic newborn, depending on chorioamnionitis prevalence. CONCLUSIONS: Some infants born to mothers with chorioamnionitis may have no signs of sepsis at birth despite having culture-confirmed infections. Implementation of current clinical guidelines may result in early diagnosis, but large numbers of uninfected asymptomatic infants would be treated.

Enrollment of Extremely Low Birth Weight Infants in a Clinical Research Study May Not Be Representative

BACKGROUND AND OBJECTIVE: The Surfactant Positive Airway Pressure and Pulse Oximetry Randomized Trial (SUPPORT) antenatal consent study demonstrated that mothers of infants enrolled in the SUPPORT trial had significantly different demographics and exposure to antenatal steroids compared with mothers of eligible, but not enrolled infants. The objective of this analysis was to compare the outcomes of bronchopulmonary dysplasia, severe retinopathy of prematurity, severe intraventricular hemorrhage or periventricular leukomalacia (IVH/PVL), death, and death/severe IVH/PVL for infants enrolled in SUPPORT in comparison with eligible, but not enrolled infants. METHODS: Perinatal characteristics and neonatal outcomes were compared for enrolled and eligible but not enrolled infants in bivariate analyses. Models were created to test the effect of enrollment in SUPPORT on outcomes, controlling for perinatal characteristics. RESULTS: There were 1316 infants enrolled in SUPPORT; 3053 infants were eligible, but not enrolled. In unadjusted analyses, enrolled infants had significantly lower rates of death before discharge, severe IVH/PVL, death/severe IVH/PVL (all < 0.001), and bronchopulmonary dysplasia (P = .003) in comparison with eligible, but not enrolled infants. The rate of severe retinopathy of prematurity was not significantly different. After adjustment for perinatal factors, enrollment in the trial was not a significant predictor of any of the tested clinical outcomes. CONCLUSIONS: The results of this analysis demonstrate significant outcome differences between enrolled and eligible but not enrolled infants in a trial using antenatal consent, which were likely due to enrollment bias resulting from the antenatal consent process. Additional research and regulatory review need to be conducted to ensure that large moderate-risk trials that require antenatal consent can be conducted in such a way as to ensure the generalizability of results.

Methicillin-Resistant and Susceptible Staphylococcus aureus Bacteremia and Meningitis in Preterm Infants

BACKGROUND: Data are limited on the impact of methicillin-resistant Staphylococcus aureus (MRSA) on morbidity and mortality among very low birth weight (VLBW) infants with S aureus (SA) bacteremia and/or meningitis (B/M). METHODS: Neonatal data for VLBW infants (birth weight 401–1500 g) born January 1, 2006, to December 31, 2008, who received care at centers of the Eunice Kennedy Shriver National Institute of Child Health and Human Development Neonatal Research Network were collected prospectively. Early-onset (≤72 hours after birth) and late-onset (>72 hours) infections were defined by blood or cerebrospinal fluid cultures and antibiotic treatment of ≥5 days (or death <5 days with intent to treat). Outcomes were compared for infants with MRSA versus methicillin-susceptible S aureus (MSSA) B/M. RESULTS: Of 8444 infants who survived >3 days, 316 (3.7%) had SA B/M. Eighty-eight had MRSA (1% of all infants, 28% of infants with SA); 228 had MSSA (2.7% of all infants, 72% of infants with SA). No infant had both MRSA and MSSA B/M. Ninety-nine percent of MRSA infections were late-onset. The percent of infants with MRSA varied by center (P < .001) with 9 of 20 centers reporting no cases. Need for mechanical ventilation, diagnosis of respiratory distress syndrome, necrotizing enterocolitis, and other morbidities did not differ between infants with MRSA and MSSA. Mortality was high with both MRSA (23 of 88, 26%) and MSSA (55 of 228, 24%). CONCLUSIONS: Few VLBW infants had SA B/M. The 1% with MRSA had morbidity and mortality rates similar to infants with MSSA. Practices should provide equal focus on prevention and management of both MRSA and MSSA infections among VLBW infants.

Outcomes of small for gestational age infants born at <27 weeks' gestation

OBJECTIVE To determine whether small for gestational age (SGA) infants born at <27 weeks gestational age (GA) are at increased risk for mortality, morbidity, and growth and neurodevelopmental impairment at 18-22 months corrected age. STUDY DESIGN This was a retrospective cohort study from National Institute of Child Health and Human Development Neonatal Research Networks Generic Database and Follow-Up Studies. Infants born at <27 weeks GA between January 2006 and July 2008 were included. SGA was defined as birth weight <10th percentile for GA based on Olsen growth curves. Infants with birth weight ≥ 10th percentile for GA were classified as non-SGA. Maternal and infant characteristics, neonatal outcomes, and neurodevelopmental data were compared in SGA and non-SGA infants. Neurodevelopmental impairment was defined as any of the following: cognitive score <70 on the Bayley Scales of Infant Development III, moderate or severe cerebral palsy, bilateral hearing loss (with and without amplification), or blindness (bilateral vision <20/200). Logistic regression analysis was applied to evaluate the associations between SGA status and death or neurodevelopmental impairment. RESULTS The SGA group comprised 385 infants; the non-SGA group, 2586 infants. Compared with mothers of non-SGA infants, mothers of SGA infants were more likely to have a high school education, prenatal care, cesarean delivery, pregnancy-induced hypertension, and antenatal corticosteroid exposure. Compared with non-SGA infants, SGA infants had higher mortality and were more likely to have postnatal growth failure, prolonged mechanical ventilation, and postnatal steroid use. SGA status was associated with increased risk of death or neurodevelopmental impairment (OR, 3.91; 95% CI, 2.91-5.25; P < .001). CONCLUSION SGA status in infants born at <27 weeks GA is associated with an increased likelihood of postnatal steroid use, mortality, growth failure, and neurodevelopmental impairment at 18-22 months corrected age.

Prolonged Hospital Stay for Extremely Premature Infants: Risk Factors, Center Differences, and the Impact of Mortality on Selecting a Best-Performing Center

OBJECTIVE:The first objective was to identify factors associated with prolonged hospital stay (PHS: hospitalized >42 weeks postmenstrual age) in extremely premature (EP: born less than or equal to 28 weeks gestation) infants. The second objective was to identify a PHS best-performing benchmark center.METHODS:This study was a retrospective cohort analysis of infants born ≤28 weeks gestation and admitted to one of 12 tertiary centers between January 1998 and October 2001. Risk-adjusted odds of PHS, defined as hospitalization beyond 42 weeks postmenstrual age, and the competing outcome, mortality, were assessed using logistic regression models.RESULTS:Among 3892 EP survivors who had complete data for multivariable analysis, 685 (18%) had PHS. Variables contributing to PHS included chronic lung disease (oxygen use at discharge home or 36 week postmenstrual age) (OR 6.75; 95% CI: 5.04 to 9.03), necrotizing enterocolitis requiring surgery (OR 13.83; 95% CI: 8.05 to 23.76), and >two episodes of late-onset sepsis (OR 2.39; 95% CI: 1.66 to 3.44). Centers’ risk-adjusted PHS odds differed from the reference center, which had the lowest incidence of PHS and mortality (overall P-value <0.0001). Mortality contributed to PHS, but in an opposite direction compared to other factors. Centers with lowest PHS odds were among those with highest mortality.CONCLUSIONS:These findings suggest that reduction of CLD, surgical NEC, and late onset sepsis could reduce PHS in EP infants. Risk adjusted odds of PHS and mortality are both crucial for selecting a PHS best-performing center.