Sample
The Swedish antenatal health care system is used by almost 100 % of pregnant women in the country. The antenatal and delivery care is free of charge. At the antenatal care clinics (ANC) healthy pregnant women are recommended to attend the regular antenatal programme with seven to nine visits to a midwife during pregnancy, and, if needed, extra appointments with an obstetrician and/or with the midwife. Women attending the antenatal clinic at Värnamo Hospital, a small hospital in the south of Sweden, were asked to participate. They were given written and oral information about the study by their midwife at the first visit to the antenatal clinic around gestational week 12. At the next visit (around gestational week 26) those interested in participating signed an informed consent. A total of 953 women were enrolled at the antenatal clinic during the study period. Of these, 740 women were approached and asked to participate in the study, 154 were excluded due to difficulties in understanding Swedish, and 186 declined participation. During the study period, nine women did not provide the study nurse with any hair samples and one woman changed her mind and asked to be removed from the study. Thus, 390 women were included in the study. Samples of hair were taken at around gestational week 26, at childbirth and finally at the postpartum check-up. The numbers of hair samples of sufficient quantity and quality to perform HCC analyses were: taken around gestational week 26, n=330; at childbirth, n=303; and at the postpartum control, n=311 (Figure S1). The total sample was divided into primiparous women and multiparous women in most analyses. Demographic information as well as data on mental health and use of medications are presented in Table 1.