Table 1.
Characteristics of the ITU cohort participants, in comparison to all live births in Finland between 2006 and 2017
| Maternal characteristics | ITU n=944 |
Live births in Finland between 2006 and 2017* n=670 097 |
Difference between groups† |
| Mean (SD) or n (%) | Mean (SD) or n (%) | P value | |
| Age at delivery, years, mean (SD) | 34.8 (5.0) | 30.4 (5.3) | <0.001 |
| Early-pregnancy BMI, mean (SD) | 24.1 (4.3) | 24.4 (4.9) | 0.05 |
| Primiparous, n (%) | 464 (49.2%) | 278 639 (41.6%) | <0.001 |
| Caesarean section, n (%) | 199 (21.1%) | 106 292 (15.9%) | <0.001 |
| Hypertension in pregnancy, n (%) | 66 (7.0%) | 27 732 (4.1%) | <0.001 |
| Gestational diabetes, n (%) | 191 (20.2%) | 76 220 (11.4%) | <0.001 |
| Smoking during pregnancy, n (%)‡ | 70 (7.4%) | 98 650 (14.7%) | <0.001 |
| Antenatal corticosteroid treatment, n (%) | 32 (3.4%) | 14 868 (2.2%) | 0.01 |
| Child characteristics | |||
| Sex, girl, n (%) | 460 (48.7%) | 327 535 (48.9%) | 0.93 |
| Preterm birth (<37 weeks), n (%) | 46 (4.9%) | 28 610 (4.3%) | 0.36 |
| Birth weight, g, mean (SD) | 3503 (540) | 3529 (527) | 0.15 |
% is the proportion of participants within the data.
n is the number of participants.
*Birth register data for children born in Finland between 2006 and 2007 are based on previously published data.4
†P values were calculated using Pearson Χ2 tests for categorical variables and using t-tests (equal variances not assumed) for continuous variables.
‡In the ITU study, three women had missing data on smoking during pregnancy, otherwise the data presented in this table were complete for all participants. The number of women/children in the Medical Birth Register with available data ranged across items from 656 860 to 670 097, as described previously.4
BMI, body mass index; ITU, InTraUterine sampling in early pregnancy.