These results showed that Finland has managed to decrease preterm neonatal mortality rates and keep the term mortality rates in low levels. Despite the decreased annual birth volumes and increase in the number of small volume birthing hospitals, the neonatal mortality outcomes have not worsened. These findings do not support the closure of current delivery units, as there were no clear trends based on the overall delivery unit volume, or with the delivery unit volume change. These findings indicate that the current centralization of high-risk cases have been effective. The majority of the previous literature has focused on the centralization of very preterm births or very low-birth weight neonates, and these studies have found improved survival and less morbidity in larger units [8,9,10]. The literature focusing of moderate and late preterm outcomes is more limited. One systematic review analyzed low risk births and reported an association between delivery unit volume and improved neonatal outcomes [11]. However, meta-analysis was not conducted due to major heterogeneity in the study settings and definitions. The studies had used various thresholds from 500 to 1000 in the low volume unit definition. In Finland, the threshold has been 1000 deliveries per year, and currently seven of the 23 birth hospitals in Finland have less deliveries.

A clear limitation is that this study is based on the materials available in the open-access database, and thus the reporting is limited and controlling for confounding factors was not possible. However, this may be seen also as a strength as this enables the prompt reporting, as currently due to legislation changes the waiting times to individual level datasets have been prolonged up to 12 months in Finland [12]. Furthermore, the coverage and the quality of the Finnish birth register data has been excellent [13].

These findings provide important material for the discussion on the centralization of births, and due to already ongoing centralization of high-risk pregnancies to tertiary units, the current findings of this study show no clear association between the delivery unit volume and neonatal mortality rates in Finland. These current desires to re-organize delivery units come from funding and politics in Finland. Due to changes in the healthcare organizations and continuous decrease in fertility rate in Finland, the continuous monitoring of neonatal outcomes is needed to maintain the current excellence in the care of neonates.