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.