Bibian van der Voorn

38 CHAPTER 3 been described in one study population, cortisone levels were not taken into account and the course followed by GC levels in hair postpartum has not been studied. Therefore, we aimed to describe cortisol and cortisone concentrations in neonatal hair, obtained directly postpartum, and their relation with maternal hair GC levels and pre- and perinatal factors. Finally, we explored the differences in hair GC concentrations between birth and an outpatient visit (OPV) at approximately 6 wks postpartum, as well as which factors are of influence on this difference. METHODS POPULATION From February 2012 to August 2013, mother-infant pairs were included in the OLVG West Hospital in Amsterdam, The Netherlands. Subjects were informed regarding the study before or within 24h after delivery. The infant needed to be admitted to the hospital (maternity ward or neonatal care unit) for at least 72h for a neonatal or maternal reason, as this was an inclusion criterion for a simultaneous study 19 . Subjects were excluded for the following reasons: (1) insufficient knowledge of the Dutch or English language, (2) mental retardation of one or both parents, (3) multiple pregnancy, (4) use of illicit drugs or regular (>2 IU/week) alcohol use during the last trimester, (5) use of systemic corticosteroids during pregnancy, (6) if participating in this study would interfere with regular care, or (7) use of psychotropic medication. The study was approved by the medical ethics committees of the OLVG West Hospital and the VUMC in Amsterdam, the Netherlands. Written informed consent was obtained from all participants. DETERMINANTS The mother filled in a questionnaire about demographic characteristics. Information on perinatal characteristics and the reasons for admission to the hospital were obtained from medical records. HAIR CORTISOL MEASUREMENTS On the first day postpartum neonatal hair was cut from the posterior vertex of the scalp, as close as possible to the scalp, as this region shows the least variance between different strands 14 . At the OPV around 6 wks postpartum, neonatal hair was collected again. The total length of hair directly postpartumwas analyzed, with the assumption