Table 1. Description of the SELMA and TIDES Study Populations .
| Variable | No. (%) | |
|---|---|---|
| SELMA (N = 963) | TIDES (N = 370) | |
| Child’s sex, male | 508 (52.8) | 185 (50.0) |
| Child’s sex, female | 455 (47.2) | 185 (50.0) |
| Premature birtha | 44 (4.6) | 38 (10.4) |
| Mother’s educational level: completed college or university | 629 (65.3) | 283 (76.5) |
| Mother smoked at study enrollment | 51 (5.3) | 23 (6.2) |
| Mother’s race/ethnicity: white/non-Hispanic | 963 (100) | 274 (74.1) |
| Child’s age at language assessment, median (IQR), mob | 30 (NA) | 37 (29.8-43.0) |
| Mother’s weight at study enrollment, mean (SD), kg | 70.0 (13.9) | 71.5 (17.8) |
| Gestational age at urine collection, median (IQR), wk | 10.0 (9.0-11.0) | 10.9 (9.3-12.3) |
Abbreviations: IQR, interquartile range; NA, not available; SELMA, Swedish Environmental Longitudinal Mother and Child, Asthma and Allergy study; TIDES, The Infant Development and the Environment Study.
a
Premature birth was defined as gestational age at birth of fewer than 37 weeks.
b
In the SELMA study, language development was assessed at routine pediatric visit at 30 months of age. In TIDES, language development was assessed by mailed questionnaire at 36 months of age.