Association between perinatal interventional activity and 2-year outcome of Swiss extremely preterm born infants: a population-based cohort study

Abstract

Objectives: To investigate if centre-specific levels of perinatal interventional activity were associated with neonatal and neurodevelopmental outcome at 2 years of age in two separately analysed cohorts of infants: cohort A born at 22-25 and cohort B born at 26-27 gestational weeks, respectively.

Design: Geographically defined, retrospective cohort study.

Setting: All nine level III perinatal centres (neonatal intensive care units and affiliated obstetrical services) in Switzerland.

Patients: All live-born infants in Switzerland in 2006-2013 below 28 gestational weeks, excluding infants with major congenital malformation.

Outcome measures: Outcomes at 2 years corrected for prematurity were mortality, survival with any major neonatal morbidity and with severe-to-moderate neurodevelopmental impairment (NDI).

Results: Cohort A associated birth in a centre with high perinatal activity with low mortality adjusted OR (aOR 0.22; 95% CI 0.16 to 0.32), while no association was observed with survival with major morbidity (aOR 0.74; 95% CI 0.46 to 1.19) and with NDI (aOR 0.97; 95% CI 0.46 to 2.02). Median age at death (8 vs 4 days) and length of stay (100 vs 73 days) were higher in high than in low activity centres. The results for cohort B mirrored those for cohort A.

Conclusions: Centres with high perinatal activity in Switzerland have a significantly lower risk for mortality while having comparable outcomes among survivors. This confirms the results of other studies but in a geographically defined area applying a more restrictive approach to initiation of perinatal intensive care than previous studies. The study adds that infants up to 28 weeks benefited from a higher perinatal activity and why further research is required to better estimate the added burden on children who ultimately do not survive.

Keywords: fetal medicine; neonatology; quality in health care.

Figure 1

Study population overview. GA, gestational age; NICU, neonatal intensive care unit.

Figure 2

ORs of outcome when born in a unit with high perinatal interventional activity. ORs with 95% CI of outcome when born in high activity units, crude or adjusted for GA, GA², birthweight z-score, male sex, multiple births and socioeconomic status. Dotted lines represent results received when using non-imputed data. AUC, area under receiver operator characteristic curve representing predictive validity of risk adjustment. GA, gestational age; NDI, neurodevelopmental impairment.

Figure 3

Age at death in NICU (days). Log-transformed age at death in NICU (days) for low and high activity centres in cohort A and cohort B. Crude y-axis scale on right-hand side. Violin plot: box-plot with median, IQR and density (width=frequency). GA, gestational age; NICU, neonatal intensive care unit.