Identifying the true scale of perinatal deaths

The survival of sick and preterm infants is an important outcome in many studies of neonatal intensive care 1-3. Infant survival rates are commonly compared to identify time-trends and to benchmark hospitals, regions and even countries 4. These statistics are also vital when evaluating the capacity and performance of the healthcare system 5, as well as primary outcomes in trials that look at the safety, effectiveness and efficacy of perinatal and neonatal interventions 6, 7. The problem is that a varying, and often unknown, proportion of perinatal and neonatal deaths occur outside the neonatal intensive care unit (NICU), which could make interpreting perinatal statistics more or less difficult. In this issue of Acta Paediatrica, Du Pont-Thibodeau et al. from Montreal present data on the timing and modes of perinatal deaths outside the NICU in a Canadian tertiary centre and over two, three-year periods between 2000 and 2010 8. The team reviewed 444 cases of perinatal deaths that took place at 22 or more weeks of gestation without a NICU admission. This showed that the total number of perinatal deaths outside the NICU increased, as did foeticides for congenital anomalies. However, there were also decreases in stillbirths after hospital admission and deaths following induced labour and comfort care for foetal anomalies. The authors concluded that paediatricians should be aware of the epidemiology of perinatal mortality in their own practice, as it has a direct impact on the denominator in NICU outcome studies. My view is that researchers should be equally aware of this. Although the authors acknowledged limitations in the generalisability of their findings to other settings, the paper by Du Pont-Thibodeau et al. is still important for the rest of us. It highlights denominator bias, namely the higher survival rates that are reported when only live infants admitted to the NICU form the denominator as opposed to when either all live births or all births are used 9. The magnitude of problem is well illustrated by the authors’ findings that an average of one or two perinatal deaths occurred every week outside the NICU in infants of 22 weeks of gestation or more. The majority (77%) of cases involved congenital malformations, of which an increasing proportion – 41% in the most recent study period – ended as foeticides and late terminations of pregnancies. As a Scandinavian, I note that the Canadian findings illustrate some legal and ethical disparities between countries. For example, late terminations are very rare in Sweden and foeticide is not permitted at 22 weeks of gestation or more. Likewise, termination and foeticide or induced labour because of an increased risk of prematurity, or induced labour for psychological reasons with comfort care at birth 8, would not be an option at 22 weeks of gestation or more. Therefore, it would be interesting to compare the rates of malformations among extremely preterm infants born alive. In the Extremely Preterm Infants in Sweden Study (EXPRESS), congenital anomalies were reported to affect 12% of live born infants 1, whereas the proportion of live born infants and their contributions to outcomes have been less clear in other studies 3. Other categories of perinatal deaths outside the NICU include neonatal deaths at home, after hospital discharge, and deaths occurring before or during transfers from peripheral hospitals. These cases seem to be unaccounted for in the paper by Du Pont-Thibodeau et al. In addition to deaths outside the NICU, the practice of withdrawing intensive care in the NICU is known to vary significantly between countries and regions, which may also contribute to variations in overall survival rates. EXPRESS researchers reported that 40% of deaths that occurred at least 24 hours after NICU admission involved a decision to withdraw intensive care on the basis of anticipated poor long-term prognosis 1. The present study by Du Pont-Thibodeau et al. sheds light on hidden and unknown perinatal deaths. In 2016, an expert panel published recommendations for future publications on how to improve reporting of survival after preterm birth and communicate outcomes more clearly 10. Please follow them!

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