Epidemiology of prematurity – How valid are comparisons of neonatal outcomes?

doi:10.1016/j.siny.2007.05.002

Seminars in Fetal and Neonatal Medicine

Volume 12, Issue 5, October 2007, Pages 337-343

https://doi.org/10.1016/j.siny.2007.05.002 Get rights and content

Summary

Direct comparisons of neonatal outcomes at any level (unit, regional or international), require detailed validation and standardisation to ensure ‘like for like’ evaluation. Reported variation in neonatal performance may be either real or the result of one or more artefacts of the data collection. These issues need to be understood in order for an accurate interpretation to be made. Such artefacts are a particular feature of national data collection systems and can lead to serious misinterpretation. For example, very preterm deliveries have a major impact on neonatal mortality rates in developed countries with births before 33 weeks of gestation accounting for between 35% and 70% of neonatal deaths. Variation in the rate of very preterm delivery rates and differing practices regarding registration of these infants can have a major effect on the recorded neonatal mortality rate.

At a more local level the validity of neonatal comparisons often depends upon whether the question being raised is appropriately matched to the data obtained to answer it. Problems arise when the question being addressed has been poorly framed or the data used to answer it has been inappropriately chosen. Comparisons using questions based on clearly defined standardised outcome measures and good quality prospective data collection are a much better way to proceed.

Section snippets

Background

There are two main reasons for carrying out comparisons of neonatal outcomes: (1) as an indicator of the health of mothers and babies in a population allowing for inter-regional and international comparisons, and (2) to monitor the quality of perinatal and neonatal care provision providing information for the performance management of perinatal and neonatal services.

In all countries, monitoring the wellbeing of the population is a key public health activity, which is often devolved to local

Measurement of neonatal mortality rates

There are a number of factors that have a direct effect upon the measurement of neonatal mortality rates leading to variations in reported rates that may be either real or the result of one or more artefacts in the data collection. These issues need to be investigated in order for an accurate interpretation to be made. Limitations of national data collection systems are such that this cannot easily be achieved and, therefore, misleading results can be unwittingly presented and, subsequently,

How should the measurement of neonatal mortality rates be standardised?

A simple method is required for the reporting of neonatal outcomes, in particular neonatal mortality, that takes into account the make up of the birth population, thus allowing for more valid regional and international comparisons of perinatal and neonatal health. The collection of data concerning the gestational age and birth weight for all birth outcomes from 22 weeks' gestational age allows the production of gestational age and birth weight-specific survival or mortality charts for

Neonatal outcome measures to assess clinical performance

It seems now to be a ‘given’ that all medical practitioners should be able to demonstrate the quality of what they do (performance management). Similarly there is an expectation amongst the public that the medical services available to them should be able to produce evidence of the fact that they are as good as those elsewhere (bench marking).³² However, many of the problems described above with regard to the comparison of distinct populations are shared by these more local and specific

Recommendations

The title of this article posed a question, ‘…how valid are comparisons of neonatal outcomes?’ The answer would appear to be ‘perfectly valid’ if the question being raised and the data obtained to answer it are appropriately matched. Where problems arise it is often that the question being addressed has been poorly framed or the data used to answer have been inappropriately chosen. We do need new approaches to this whole area recognising, for example, that traditional perinatal, neonatal and

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Cited by (14)

Pronostic risk assessment of delivery, in patients admitted for threatened preterm birth, in a tertiary care maternity center
2014, Journal de Gynecologie Obstetrique et Biologie de la Reproduction
Déterminer le taux d’accouchement prématuré (AP) des patientes hospitalisées pour menace d’accouchement prématuré (MAP) dans une maternité de niveau III, afin d’évaluer nos outils diagnostiques et notre prise en charge thérapeutique.
Étude de cohorte rétrospective de toutes les patientes hospitalisées pour MAP dans une maternité de niveau III (Marseille, France) du 1^er janvier 2009 au 31 décembre 2009.
Nous avons colligé 224 hospitalisations pour MAP avec 181 grossesses uniques (GU) et 43 grossesses gémellaires (GG), Les transferts materno-fœtaux représentaient 43,8 % de l’ensemble des hospitalisations pour MAP dans notre centre. Le taux global d’AP était de 44,9 % (n = 89), de 39 % pour les GU (n = 66) et de 76,6 % (n = 23) pour les GG. Le seuil de 15 mm pour la mesure échographique de longueur cervicale (LC) était le plus pertinent pour prédire le risque d’AP, avec 77,3 % (85/110) des patientes ayant une LC > 15 mm qui ont accouché à terme.
En cas de grossesse unique, la majorité des patientes avec une LC > 15 mm accouchent à terme. Ainsi, il semble nécessaire de développer l’utilisation d’autres marqueurs prédictifs plus performants de risque de travail prématuré, pour améliorer le diagnostic et la prise en charge des MAP.
To assess preterm birth rate, in patients admitted for threatened preterm birth (TPB) in a tertiary care maternity center and evaluate our diagnostic and therapeutic tools.
A retrospective cohort study, in a tertiary care maternity center (Marseille, France), reviewed all admissions for TPB from January 1 to December 31, 2009.
We recorded 224 admissions for TPB (181 single pregnancies and 43 twin pregnancies), 43.8% of TPB admissions were from materno-fetal transfer. Preterm birth rate was 44.9% (n = 89), 39% (n = 66) for single pregnancy and 76.6% (n = 23) for twins. The 15 mm threshold for transvaginal sonography cervical length (CL) was the most relevant to predict the risk of preterm delivery, 77.3% (85/110) of patients with CL > 15 mm having full term delivery.
For single pregnancy, most of the patients with cervical length > 15 mm have full term delivery. It seems important to us to develop the use of more efficient predictive markers of risk-premature labor in order to improve the diagnosis and management of TPB.
Outcomes following periviable birth
2014, Seminars in Perinatology
Citation Excerpt :
A major difficulty in interpreting published outcomes is that decisions regarding intensive care vs. palliative care are carried out at multiple junctures—prior to birth, in the delivery room, and in NICUs.14–17 Outcome statistics following periviable birth are highly dependent on the denominator used.18–20 Figure 3 from Guillen and colleagues’ systematic review of published survival rates for ELBW newborns demonstrates that omitting ELBW newborns treated with comfort care from denominators will greatly exaggerate survival rates.18
This review is presented in three segments: (1) important background concepts, (2) recent reports from regional geographically defined cohorts, and (3) prognosis research from the National Institutes of Health Neonatal Research Network. Extending the use of intensive care to newborns of lower gestational ages will unavoidably result in a higher proportion and a higher absolute number of survivors with morbidity, unless other changes in practice offset the increased risk associated with decreasing gestational age. In geographically defined cohort studies, the proportion of periviable newborns delivered in perinatal centers and the practices around foregoing and withdrawing intensive care are two important determinants of outcomes following periviable birth. It is much easier to quantify the effect of the former than the latter. Decisions regarding comfort care vs. intensive are frequently based on gestational age as the sole predictor variable, although multiple factors can be readily used to more accurately assess the benefits and burdens of intensive care and facilitate better informed parental counseling and decision making.
Variables determining the amount of care for very preterm neonates: The concept of medical stance
2014, Archives de Pediatrie
Comparer la quantité de soins délivrés aux prématurés de 24–31 semaines d’aménorrhée (SA) 0/6j nés dans deux centres hospitalo-universitaires de niveau III, un centre étant engagé dans les soins de soutien au développement, l’autre non. L’objectif secondaire était d’apprécier si la différence de la quantité de soins délivrés s’accompagnait d’une différence de morbi-mortalité hospitalière.
Les 1286 grands prématurés de 24–31 SA 0/6j nés vivants, indemnes de malformation létale et hospitalisés dans ces deux centres ont été inclus de façon prospective de 2006 à 2010. La quantité de soins délivrés a été appréciée par la mesure de 5 interventions : la naissance par césarienne, l’intubation en salle de naissance, l’administration de surfactant, le traitement du canal artériel, la transfusion de globules rouges.
Les 5 interventions étaient plus souvent proposées par le centre ne proposant pas de soins de soutien au développement. Si les taux de survie sans anomalie neurologique sévère à l’imagerie avant le retour à domicile étaient comparables, le taux de dysplasie broncho- pulmonaire, la durée de séjour hospitalier, et le taux d’infections nosocomiales étaient plus élevés dans le centre le plus interventionniste.
Cette étude souligne qu’il n’existait pas en France, dans les années de l’étude, une unique façon de traiter les grands prématurés. Le « plus » de soins observés dans un des deux centres suggère une notion que nous appellerons « regard médical ». Il s’agit d’une dimension située en amont de la prise en charge, qui fait préférer aux équipes médicales tel ou tel type de prise en charge. Nous discutons les paramètres susceptibles de structurer ce regard médical. Dans un autre domaine mais avec prudence, ce travail pose la question de l’interprétation d’une démarche de comparaison des pratiques, lorsqu’une augmentation de la morbidité est observée là où la logique des procédures conduit au « plus » d’interventions.
To compare the amount of medical interventions on very preterm neonates (24–31 weeks of gestation) in two French university tertiary care centers, one of which is involved in a Neonatal Developmental Care program. A secondary objective is to assess whether this difference in medical interventions can be linked to a difference in mortality and morbidity rates.
We prospectively included all very preterm neonates free from lethal malformation born live in these two centers between 2006 and 2010. These inclusion criteria were met by 1286 patients, for whom we compared the rate of five selected medical interventions: birth by caesarean section, chest intubation in the delivery room, surfactant therapy, pharmacological treatment of patent ductus arteriosus, and red blood cell transfusion.
The rates of the five medical interventions were systematically lower in the center that is involved in Neonatal Developmental Care. There was no significant difference in survival at discharge with no severe cerebral ultrasound scan abnormalities between the two centers. There were, however, significantly higher rates of bronchopulmonary dysplasia and nosocomial sepsis and longer hospital stays when the patients were not involved in a Neonatal Developmental Care program.
This benchmarking study shows that in France, in the first decade of the 21st century, there are as many ways to handle very preterm neonates as there are centers in which they are born. This brings to light the concept of medical stance, which is the general care approach prior to the treatment itself. This medical stance creates the overall framework for the staff's decision-making regarding neonate care. The different parameters structuring medical stance are discussed. Moreover, this study raises the problematic issue of the aftermath of benchmarking studies when the conclusion is an increase of morbidity in cases where procedure leads to more interventions.
Survival rates in extremely low birthweight infants depend on the denominator: Avoiding potential for bias by specifying denominators
2011, American Journal of Obstetrics and Gynecology
Citation Excerpt :
Evans and Levene8 recommended that a set of minimum criteria should be considered for future publications. More recently Draper and Field7 argued that direct comparisons of neonatal outcomes could not be made in the setting of unclear definitions. Despite these concerns, marked variation in the denominators used to calculate survival persists into the era of this current study: 2000-2010.
The objective of the study was to assess whether recent data reporting survival of preterm infants introduce a bias from the use of varying denominators.
We performed a systematic review of hospital survival of infants less than 1000 g or less than 28 weeks. Included publications specified the denominator used to calculate survival rates.
Of 111 eligible publications only 51 (46%) specified the denominators used to calculate survival rates: 6 used all births, 25 used live births, and 20 used neonatal intensive care unit admissions. Overall rates of survival to hospital discharge ranged widely: from 26.5% to 87.8%. Mean survival varied significantly by denominator: 45.0% (±11.6) using a denominator of all births, 60.7% (±13.2) using live births, or 71.6% (±12.1) using used neonatal intensive care unit admissions (P ≤ .009 or less for each of 3 comparisons).
Variations in reported rates of survival to discharge for extremely low-birthweight (<1000 g) and extremely low-gestational-age (<28 weeks) infants reflect in part a denominator bias that dramatically affects reported data.
Neonatal and perinatal mortality in hospitals of the Basque Country-Navarre Neonatal Study Group (GEN-VN) during the period 2000-2006
2009, Anales de Pediatria
el Grupo de Estudios Neonatales Vasco-Navarro (GEN-VN) se creó en el año 2000 para estudiar y contribuir a mejorar los resultados de la asistencia de los recién nacidos de Navarra y el País Vasco.
presentar la evolución de las tasas de mortalidad perinatal y neonatal de los hospitales participantes en el GEN-VN en el periodo de 2000 a 2006 y analizar sus causas.
estudio descriptivo con base poblacional de los 157.623 nacimientos de los hospitales del GEN-VN en un periodo de 7 años (2000-2006). De ellos, 156.904 nacieron vivos y hubo 719 muertes fetales y 363 muertes neonatales. Se analizó la mortalidad perinatal y neonatal, bruta y específica por grupos de peso y edad gestacional.
el GEN-VN recogió entre un 80,5 y un 96,8% del total de nacimientos que declararon las administraciones de Navarra y País Vasco. Las tasas de mortalidades fetal y perinatal mostraron una tendencia decreciente, mientras que la mortalidad neonatal está estabilizada por encima del 2‰, en comparación con el descenso observado durante los últimos años del siglo xx. Las causas más frecuentes de mortalidad fueron las infecciones, la insuficiencia respiratoria y las anomalías congénitas.
la recogida regional de datos aumenta la calidad de los estudios de mortalidad perinatal y neonatal, al tener una base poblacional. Los recién nacidos de muy bajo peso y muy baja edad gestacional requieren una atención especializada debido a la alta mortalidad, que representa el 54,8% de la mortalidad neonatal (año 2006).
In 2000, the Basque-Navarre Neonatal Study Group (GEN-VN) was created with a clear objective of studying the perinatal and neonatal health outcomes in newborns.
The aim of this investigation is to present the trends of neonatal and perinatal mortality and their causes in the hospitals of the Basque-Navarre Neonatal Study Group from 2000 to 2006.
A descriptive study was carried out on the 157,623 births in the participating hospitals of the Basque-Navarre Neonatal Study Group, from 2000 to 2006. During this period, of the total births, 156.904 were born alive, there were 719 foetal deaths and 363 newborns died within the first 28 days of life. Perinatal and neonatal mortality was analysed, raw and stratified by gestational age and birth weight.
The Basque -Navarre Neonatal Study Group collects from 80.5% to 96.8% of all the births reported by the authorities. There is a decreasing trend in foetal and perinatal mortality rates from 2000 to 2006. However, neonatal mortality rates shows a stable trend when compared with the descense in the last years of the 20th century. The most frequent causes of death are respiratory, infections and the congenital anomalies.
Collecting regional data improves the quality of neonatal and perinatal mortality studies. Very low birth weight and very low gestational age newborns require special quality of care due their high mortality (54.8% of neonatal mortality in 2006), therefore further studies are required on the impact of these newborns on neonatal mortality in our hospitals.
How can we make international comparisons of infant mortality in high income countries based on aggregate data more relevant to policy?
2017, BMC Pregnancy and Childbirth

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Epidemiology of prematurity – How valid are comparisons of neonatal outcomes?

Summary

Section snippets

Background

Measurement of neonatal mortality rates

How should the measurement of neonatal mortality rates be standardised?

Neonatal outcome measures to assess clinical performance

Recommendations

Eur J Obstet Gynecol Reprod Biol

Eur J Obstet Gynecol Reprod Biol

Early Hum Dev

Lancet

Lancet

Baillière's Clin Obstet Gynaecol

BJOG

Lancet

J Pediatr

Prediction of survival for preterm births by weight and gestational age: retrospective population based study

BMJ

The search for perinatal definitions and standards

Acta Paediatr Scand

PERISTAT: indicators for monitoring and evaluating perinatal health in Europe

Eur J Public Health

The undesirable consequences of controlling for birth weight in perinatal epidemiological studies

J Epidemiol Community Health

Registration artifacts in international comparisons of infant mortality

Paediatr Perinat Epidemiol

The reliability of perinatal and neonatal rates: differential under-reporting in linked professional registers vs. Dutch civil registers

Paediatr Perinat Epidemiol

Withholding/withdrawing treatment from neonates: legislation and official guidelines across Europe

J Med Ethics

Proactive management promotes outcome in extremely preterm infants: a population-based comparison of two perinatal management strategies

Pediatrics