Bibian van der Voorn

40 CHAPTER 3 Results with a P value <0.05 were considered to be statistically significant, although borderline statistically significant results (0.10 > P > 0.05) when found for both cortisol and cortisone were also further explored. RESULTS POPULATION A total of 107 mother-infant pairs donated hair directly postpartum. At the OPV, 72 mother-infants pairs donated hair. The OPV took place at 44±11 days postpartum (range: 22 to 87 days). Perinatal and demographic characteristics are presented in Table 1 . TABLE 1. Baseline characteristics of the study population (n=107) Mean ± SD, median (range) or n (%) Perinatal Gestational age 39.5 ± 1.8, 39.5 (33.9 to 42.1) Birth weight 3480 ± 629, 3569 (1806 to 5290) Male sex 61 (55.5) Vaginal delivery 40 (32.5) Perinatal infection 34 (30.9) Respiratory problems 9 (8.2) Maternal Age 33.9 ± 4.8, 34 (21 to 44) Nulliparae 67 (54.5) Hypertensive disorders 7 (6.4) Non-Dutch ethnicity 52 (47.3) Smoking 2 (1.8) Concentration of GCs in neonatal hair Results are displayed in Table 2 and Figure 1 . Directly postpartum, the median concentration of cortisol was 169 pg/mg (range: 51 to 1294), while the median concentration of cortisone was 85 pg/mg (range: 23 to 597). Maternal GC levels were much lower than neonatal levels, with median concentrations of 5 (range: 0 to 672) and 18 (range: 2 to 87) pg/mg respectively. Course of GC levels postpartum Between birth and the OPV, a steep decrease in cortisol concentrations in infant hair was observed ( Table 2 and Figure 1 ). Maternal hair cortisol levels showed a subtle decrease between birth and the OPV. In contrast, infant and maternal hair cortisone levels remained stable, although a wide range of values were observed. At the OPV, both infant cortisol and cortisone concentrations were still higher than the GC levels