Cohort and trajectory group characteristics
A total of 9,058 pregnancies were included in this study (Figure S2). The characteristics of the pregnancies included and those lost-to-follow-up are shown in Table S1, and the characteristics of participants stratified by cohort are shown in Table S2. Calcium-based antacid use in gestational weeks 0-33 was reported in 21.1% of pregnancies. Women who used calcium-based antacids in gestational weeks 0-33 seemed to be more likely to have a high level of education, to have asthma, to be primiparous, and to have used calcium-containing supplements compared to non-users (Table 1). In 3.8% of pregnancies, PPI use in gestational weeks 0-33 was reported, with exposed women being more likely to have a low/intermediate level of education, asthma, depression, and a higher BMI, while more exposed women smoked in pregnancy, but fewer used alcohol. Late-onset preeclampsia was diagnosed in 2.6% of pregnancies at a mean gestational age of 37+6 weeks.
Two trajectories best described intake of calcium from antacids in the first 33 weeks of gestation (Figure 1). The low use trajectory is characterized by negligible use in the first 15 weeks of pregnancy, with moderate intake thereafter, whereas the high use trajectory showed a steep increase in dose after the first trimester up to 2,500-3,250 mg/day after gestational week 17. Maternal and pregnancy characteristics of the trajectory groups are shown in Table S3. In the longitudinal cluster analyses, we did not identify trajectories describing intake of calcium from antacids in gestational weeks 0-16 and 17-33 separately or trajectories that described PPI use that fulfilled the selection criteria.