Dear Editor
We are grateful to Dr Ehrhardt for his response to our recent
paper.(1) It is certainly true that the populations compared are indeed
very different, which generally makes any such comparison fraught with
potential problems in interpretation. However, we would respectfully
point out that we made some allowance for this in our analysis of place of
booking and outcomes. This quite clearly shows advantage to women booking
in Level 3 Services, compared to those booking in Level 2 services whether
or not they were transferred (aOR: 0.79 (0.63; 0.98)).
In a related paper using more recent national data and instrumental
variables using the nearest hospital to the mother's residence to describe
the base populations, we also come to the same conclusion for this group
of extremely preterm births.(2)
Although not perfect corrections for a complex situation these two
findings provide some reassurance that our conclusions are valid.
Yours sincerely
Neil Marlow
1. Marlow N, Bennett C, Draper ES, et al. Perinatal outcomes for
extremely preterm babies in relation to place of birth in England: The
EPICure 2 Study. Archives of Disease in Childhood Fetal and Neonatal
Edition 2014;99:F181-8
2. Watson SI, Arulampalam W, Petrou S, et al. The effects of
designation and volume of neonatal care on mortality and morbidity
outcomes of very preterm infants in England: retrospective population-
based cohort study. BMJ Open 2014;4(7):e004856.
Conflict of Interest:
Author of original paper
Dear Editor
We are grateful to Dr Ehrhardt for his response to our recent paper.(1) It is certainly true that the populations compared are indeed very different, which generally makes any such comparison fraught with potential problems in interpretation. However, we would respectfully point out that we made some allowance for this in our analysis of place of booking and outcomes. This quite clearly shows advantage to women booking in Level 3 Services, compared to those booking in Level 2 services whether or not they were transferred (aOR: 0.79 (0.63; 0.98)).
In a related paper using more recent national data and instrumental variables using the nearest hospital to the mother's residence to describe the base populations, we also come to the same conclusion for this group of extremely preterm births.(2)
Although not perfect corrections for a complex situation these two findings provide some reassurance that our conclusions are valid.
Yours sincerely Neil Marlow
1. Marlow N, Bennett C, Draper ES, et al. Perinatal outcomes for extremely preterm babies in relation to place of birth in England: The EPICure 2 Study. Archives of Disease in Childhood Fetal and Neonatal Edition 2014;99:F181-8
2. Watson SI, Arulampalam W, Petrou S, et al. The effects of designation and volume of neonatal care on mortality and morbidity outcomes of very preterm infants in England: retrospective population- based cohort study. BMJ Open 2014;4(7):e004856.
Conflict of Interest:
Author of original paper