Bibian van der Voorn

56 CHAPTER 4 scored for mothers who sought advice at the POP clinic. In addition, within 12 - 36h pp the HADS was scored for all participating mothers. USE OF SELECTIVE ANTIDEPRESSANTS (SADS) When admitted to the maternity ward pp, mothers were asked whether they used SADs during at least the last two weeks of pregnancy. In our cohort, 65mothers (39%) reported using either selective serotonin reuptake inhibitors (SSRIs), serotonin- norepinephrine reuptake inhibitors (SNRIs), noradrenergic and specific serotonin antidepressants (NaSSAs), or a combination of these. HAIR GLUCOCORTICOID LEVELS Mother-infant pairs donated hair on the first day pp. A lock of hair was cut from the posterior vertex as close as possible to the scalp. A minimum of 1.25mg of hair was needed for a reliable measurement. Fetal hair growth velocity and the timing of transition fromlanugoviavellus into terminal hair strands varies significantlybetween infants 25 . Therefore, the total length of neonatal hair was analyzed and mean cortisol and cortisone levels, per mg hair, were calculated. Of maternal hair, the centimeter closest to the scalp was analyzed, representing mean cortisol and cortisone levels during the last month of pregnancy, as adult hair grows approximately 1 centimeter per month 16,26 . Hair cortisol and cortisone levels were measured as described previously by Noppe and De Rijke et al. 13 . In short, hair was washed with isopropanol and hair GCs were extracted using methanol and solid-phase extraction. Subsequently, cortisol and cortisone concentrations were quantified by LC-MS/MS (Waters XEVO-TQ-S system, Waters Corporation, Milford, MA, USA), with positive electrospray ionization, and reported in pg/mg hair. DATA ANALYSIS Maternal and neonatal characteristics were compared between patients from the POP clinic and mothers admitted for other neonatal or maternal medical reasons, using independent t-test, Chi Square or Fisher exact tests. Hair cortisol and cortisone levels were skewed to the right and therefore logarithmically transformed prior to analysis. Linear regression was used to assess the association between HADS-scores and neonatal or maternal hair GC levels. The influence of maternal stress was assessed with hair GC levels as dependent factor, and HAS or HDS subscores as independent factor, continuously or dichotomously, with a score of ≥8 points as cut-off for elevated stress 23 . When significant associations