Spline figures showing non-linear associations of gestational age and birth weight with mortality (A, B) and with adverse outcome (C, D). The birth weight z-score (A, C) and the gestational age in weeks (B, D) are given on the X-axis. Each mark on the X-axis represents a patient. In panel B and D the duration of gestational age was rounded to one decimal. The natural logarithm of the multivariate Odd’s ratio for the respective outcome is shown (y-axis and solid line) with the 95%-confidence intervals (dashed lines).
Schlapbach et al. BMC Pediatrics 2012 12:198 doi:10.1186/1471-2431-12-198