Sarah E Seaton

Neurodevelopmental outcomes following late and moderate prematurity: a population-based cohort study

Objective There is a paucity of data relating to neurodevelopmental outcomes in infants born late and moderately preterm (LMPT; 32+0–36+6 weeks). This paper present the results of a prospective, population-based study of 2-year outcomes following LMPT birth. Design 1130 LMPT and 1255 term-born children were recruited at birth. At 2 years corrected age, parents completed a questionnaire to assess neurosensory (vision, hearing, motor) impairments and the Parent Report of Childrens Abilities-Revised to identify cognitive impairment. Relative risks for adverse outcomes were adjusted for sex, socio-economic status and small for gestational age, and weighted to account for over-sampling of term-born multiples. Risk factors for cognitive impairment were explored using multivariable analyses. Results Parents of 638 (57%) LMPT infants and 765 (62%) controls completed questionnaires. Among LMPT infants, 1.6% had neurosensory impairment compared with 0.3% of controls (RR 4.89, 95% CI 1.07 to 22.25). Cognitive impairments were the most common adverse outcome: LMPT 6.3%; controls 2.4% (RR 2.09, 95% CI 1.19 to 3.64). LMPT infants were at twice the risk for neurodevelopmental disability (RR 2.19, 95% CI 1.27 to 3.75). Independent risk factors for cognitive impairment in LMPT infants were male sex, socio-economic disadvantage, non-white ethnicity, preeclampsia and not receiving breast milk at discharge. Conclusions Compared with term-born peers, LMPT infants are at double the risk for neurodevelopmental disability at 2 years of age, with the majority of impairments observed in the cognitive domain. Male sex, socio-economic disadvantage and preeclampsia are independent predictors of low cognitive scores following LMPT birth.

Population-Based Estimates of In-Unit Survival for Very Preterm Infants

BACKGROUND: Estimates of the probability of survival of very preterm infants admitted to NICU care are vital for counseling parents, informing care, and planning services. In 1999, easy-to-use charts of survival according to gestation, birth weight, and gender were published in the United Kingdom. These charts are widely used in clinical care and for benchmarking survival, and they form the core of the Clinical Risk Index for Babies II score. Since their publication, the survival of preterm infants has improved, and the charts therefore need updating. METHODS: A logistic model was fitted with gestational age, birth weight, and gender. Nonlinear functions were estimated by using fractional polynomials. Bootstrap methods were used to assess the internal validity of the final model. The final model was assessed both overall and for subgroups of infants by using Farrington’s statistic, the c-statistic, Cox regression coefficients, and the Brier score. RESULTS: A total of 2995 white singleton infants born at 23+0 to 32+6 weeks’ gestation in 2008 through 2010 were identified; 2751 (91.9%) infants survived to discharge. A prediction model was estimated and good model fit confirmed (area under receiver-operating characteristics curve = 0.86). Survival ranged from 27.7% (23 weeks) to 99.1% (32 weeks) for boys and from 34.5% (23 weeks) to 99.3% (32 weeks) for girls. Updated charts were produced showing estimated survival according to gestation, birth weight and gender, together with contour plots displaying points of equal survival. CONCLUSIONS: These survival charts have been updated and will be of use to clinicians, parents, and managers.

Infants born late/moderately preterm are at increased risk for a positive autism screen at 2 years of age.

OBJECTIVES To assess the prevalence of positive screens using the Modified Checklist for Autism in Toddlers (M-CHAT) questionnaire and follow-up interview in late and moderately preterm (LMPT; 32-36 weeks) infants and term-born controls. STUDY DESIGN Population-based prospective cohort study of 1130 LMPT and 1255 term-born infants. Parents completed the M-CHAT questionnaire at 2-years corrected age. Parents of infants with positive questionnaire screens were followed up with a telephone interview to clarify failed items. The M-CHAT questionnaire was re-scored, and infants were classified as true or false positives. Neurosensory, cognitive, and behavioral outcomes were assessed using parent report. RESULTS Parents of 634 (57%) LMPT and 761 (62%) term-born infants completed the M-CHAT questionnaire. LMPT infants had significantly higher risk of a positive questionnaire screen compared with controls (14.5% vs 9.2%; relative risk [RR] 1.58; 95% CI 1.18, 2.11). After follow-up, significantly more LMPT infants than controls had a true positive screen (2.4% vs 0.5%; RR 4.52; 1.51, 13.56). This remained significant after excluding infants with neurosensory impairments (2.0% vs 0.5%; RR 3.67; 1.19, 11.3). CONCLUSIONS LMPT infants are at significantly increased risk for positive autistic screen. An M-CHAT follow-up interview is essential as screening for autism spectrum disorders is especially confounded in preterm populations. Infants with false positive screens are at risk for cognitive and behavioral problems.

Neonatal outcomes and delivery of care for infants born late preterm or moderately preterm: a prospective population-based study

Objective To describe neonatal outcomes and explore variation in delivery of care for infants born late (34–36  weeks) and moderately (32–33 weeks) preterm (LMPT). Design/setting Prospective population-based study comprising births in four major maternity centres, one midwifery-led unit and at home between September 2009 and December 2010. Data were obtained from maternal and neonatal records. Participants All LMPT infants were eligible. A random sample of term-born infants (≥37 weeks) acted as controls. Outcome measures Neonatal unit (NNU) admission, respiratory and nutritional support, neonatal morbidities, investigations, length of stay and postnatal ward care were measured. Differences between centres were explored. Results 1146 (83%) LMPT and 1258 (79% of eligible) term-born infants were recruited. LMPT infants were significantly more likely to receive resuscitation at birth (17.5% vs 7.4%), respiratory (11.8% vs 0.9%) and nutritional support (3.5% vs 0.3%) and were less likely to be fed breast milk (64.2% vs 72.2%) than term infants. For all interventions and morbidities, a gradient of increasing risk with decreasing gestation was evident. Although 60% of late preterm infants were never admitted to a NNU, 83% required medical input on postnatal wards. Clinical management differed significantly between services. Conclusions LMPT infants place high demands on specialist neonatal services. A substantial amount of previously unreported specialist input is provided in postnatal wards, beyond normal newborn care. Appropriate expertise and planning of early care are essential if such infants are managed away from specialised neonatal settings. Further research is required to clarify optimal and cost-effective postnatal management for LMPT babies.

Babies born at the threshold of viability: changes in survival and workload over 20 years.

Objective To assess the care given to the babies born at the threshold of viability over the last 20 years using regional and national data. Design Population-based retrospective study. Setting Former ‘Trent’ health region. Participants Babies born between 1 January 1991 and 31 December 2010 at 22+0 to 25+6 weeks gestational age. Main outcome measure Survival and use of respiratory support. Methods Data of all babies born between 1 January 1991 and 31 December 2010 with a gestational age of 22+0 to 25+6 weeks and admitted to a neonatal unit were extracted from The Neonatal Survey. Use of respiratory support in terms of ventilation and continuous positive airway pressure (CPAP) for this group of babies was calculated as a proportion of the total used by the whole neonatal intensive care population within the defined study area. Results The proportion of babies surviving to discharge increased significantly over time in those born at 24 and 25 weeks (p<0.01) but failed to achieve statistical significance for those at 23 weeks (p=0.08). No babies born at 22 weeks survived. The babies born at 22–25 weeks accounted for 26.3% of all ventilation and 21.5% of CPAP given. Conclusion Our work concurs with the current UK guidelines. There could be advantages in focusing the care of babies born at 23 weeks to a small number of intensive care units to allow specialist expertise to develop in all aspects of the management of these babies. However, focusing care will not necessarily improve survival or reduce morbidity.

Economic costs associated with moderate and late preterm birth: a prospective population-based study.

We sought to determine the economic costs associated with moderate and late preterm birth.

What is the probability of detecting poorly performing hospitals using funnel plots

Recent high profile cases in the UK have highlighted the impact that the reporting of clinical outcomes can have for healthcare providers and patients. Great importance has been placed on the use of statistical methods to identify healthcare providers with observed poor performance. Such providers are highlighted as potential outliers and the possible causes investigated. It is crucial, therefore, that the methods used for identifying outliers are correctly understood and interpreted. While patients, funders, managers and clinical teams really want to know the true underlying performance of the provider, this true performance generally cannot be known directly and must be estimated using observed outcomes. However, differences between the true and observed performance are likely to arise due to chance variation. Clinical outcomes are often reported through the standardised mortality ratio (SMR), displayed using funnel plots. Providers whose observed SMR falls outside the funnel plot control limits will be identified as potential outliers. However, while it is obviously desirable that a healthcare provider with a true underlying performance different from that expected should be identified, the actual probability that it will be identified from observed SMRs has not previously been described. Here we show that funnel plots for the SMR should be used with caution when the expected number of events is small as the probability of identifying providers with true poor performance is likely to be small. On the other hand, when the expected number of events is large, care must be taken as a provider may be identified as an outlier even when its divergence is of little or no clinical importance.

Birthweight Centile Charts for South Asian Infants Born in the UK

Background: UK-born infants of South Asian ethnic origin are known to have lower birthweights than their White British counterparts. When plotted on currently used birthweight charts they can be misclassified as small for gestational age. Similarly, large for gestational age infants can be missed. This has important clinical implications in their management. Objective: To create birthweight centile charts for the UK-born South Asian infants to identify true small and large for gestational age infants. Methods: A retrospective cross-sectional analysis of infants born 1 January 2003 to 31 December 2006 was undertaken. The birthweights of the South Asian and White British infants were compared. The LMS method was used to construct centile charts for the South Asian infants. Results: 24,274 White British and 7,190South Asian infants were included in the analysis. Overall, the South Asian males were 9–15% lighter than the White British males and the South Asian females were 9–13% lighter than the White British females. At term, the median birthweight for South Asian males was 329 g lower than that for White British males and for South Asian females 295 g less than the White British females. Conclusion: There are significant differences in the birthweights of White British and UK-born South Asian infants. Hence the standard birthweight centile charts which were designed using the birthweight data of White British infants appear to misclassify a proportion of South Asian infants. Use of ethnic specific birthweight charts would allow better detection of truly growth-restricted and macrosomic South Asian infants.

Socioeconomic inequalities in the rate of stillbirths by cause: a population-based study

Objective To assess time trends in socioeconomic inequalities in overall and cause-specific stillbirth rates in England. Design Population-based retrospective study. Setting England. Participants Stillbirths occurring among singleton infants born between 1 January 2000 and 31 December 2007. Main outcome measure Cause-specific stillbirth rate per 10 000 births by deprivation tenth and year of birth. Deprivation measured using the UK index of multiple deprivation at Super Output Area level. Methods Poisson regression models were used to estimate the relative deprivation gap (comparing the most and least deprived tenths) in rates of stillbirths (overall and cause-specific). Excess mortality was calculated by applying the rates seen in the least deprived tenth to the entire population at risk. Discussions with our local NHS multicentre ethics committee deemed that this analysis of national non-identifiable data did not require separate ethics approval. Results There were 44 stillbirths per 10 000 births, with no evidence of a change in rates over time. Rates were twice as high in the most deprived tenth compared with the least (rate ratio (RR) 2.1, 95% CI 2.0 to 2.2) with no evidence of a change over time. There was a significant deprivation gap for all specific causes except mechanical events (RR 1.2, 95% CI 0.9 to 1.5). The widest gap was seen for stillbirths due to antepartum haemorrhages (RR 3.1, 95% CI 2.8 to 3.5). No evidence of a change in the rate of stillbirth or deprivation gap over time was seen for any specific cause. Conclusion A wide deprivation gap exists in stillbirth rates for most causes and is not diminishing. Unexplained antepartum stillbirths accounted for 50% of the deprivation gap, and a better understanding of these stillbirths is necessary to reduce socioeconomic inequalities.

The probability of being identified as an outlier with commonly used funnel plot control limits for the standardised mortality ratio

BackgroundEmphasis is increasingly being placed on the monitoring of clinical outcomes for health care providers. Funnel plots have become an increasingly popular graphical methodology used to identify potential outliers. It is assumed that a provider only displaying expected random variation (i.e. ‘in-control’) will fall outside a control limit with a known probability. In reality, the discrete count nature of these data, and the differing methods, can lead to true probabilities quite different from the nominal value. This paper investigates the true probability of an ‘in control’ provider falling outside control limits for the Standardised Mortality Ratio (SMR).MethodsThe true probabilities of an ‘in control’ provider falling outside control limits for the SMR were calculated and compared for three commonly used limits: Wald confidence interval; ‘exact’ confidence interval; probability-based prediction interval.ResultsThe probability of falling above the upper limit, or below the lower limit, often varied greatly from the nominal value. This was particularly apparent when there were a small number of expected events: for expected events ≤50 the median probability of an ‘in-control’ provider falling above the upper 95% limit was 0.0301 (Wald), 0.0121 (‘exact’), 0.0201 (prediction).ConclusionsIt is important to understand the properties and probability of being identified as an outlier by each of these different methods to aid the correct identification of poorly performing health care providers. The limits obtained using probability-based prediction limits have the most intuitive interpretation and their properties can be defined a priori. Funnel plot control limits for the SMR should not be based on confidence intervals.