Table 2.
Description of the Covariates (Sex, Maternal Age, Socioeconomic Status) According to Birth Order (Firstborns vs. Others) Among Brazilian Adolescents in the 1993 Pelotas Birth Cohort
| Variable | Firstborns |
Others |
P Value | ||
| % | Mean (SD) | % | Mean (SD) | ||
| Sex | 0.063a | ||||
| Male | 58.7 | 49.4 | |||
| Female | 41.3 | 50.7 | |||
| Maternal age, years | <0.001a | ||||
| <20 | 29.4 | 5.8 | |||
| 20–34 | 65.7 | 81.0 | |||
| ≥35 | 4.9 | 13.2 | |||
| Maternal age, years | 23.2 (5.9) | 27.7 (5.8) | <0.001b | ||
| Quartile of family income | 0.20a | ||||
| 1 (poorest) | 22.1 | 29.4 | |||
| 2 | 25.0 | 24.1 | |||
| 3 | 25.7 | 26.8 | |||
| 4 (wealthiest) | 27.1 | 19.8 | |||
| Family income, Brazilian realc | 4.0 (4.0) | 3.7 (4.1) | 0.10d | ||
| Quartile of maternal height | 0.24a | ||||
| 1 (shortest) | 24.1 | 30.3 | |||
| 2 | 27.7 | 28.3 | |||
| 3 | 24.1 | 24.8 | |||
| 4 (tallest) | 24.1 | 16.6 | |||
| Maternal height, cm | 161.0 (7.3) | 159.6 (6.5) | 0.04b | ||
| Maternal schooling, years | <0.001a | ||||
| 0–4 | 14.7 | 33.3 | |||
| 5–8 | 51.8 | 46.6 | |||
| ≥9 | 33.6 | 20.1 | |||
| Maternal schooling, years | 7.6 (3.3) | 6.2 (3.6) | <0.001d | ||
| Maternal BMI, kg/m2 | 0.275 | ||||
| <18.5 | 10.7 | 8.8 | |||
| 18.5–24.9 | 71.4 | 65.3 | |||
| 25.0–29.9 | 14.3 | 19.2 | |||
| ≥30.0 | 3.6 | 6.7 | |||
| Maternal BMI, kg/m2 | 22.2 (3.8) | 23.1 (3.9) | 0.034b | ||
Abbreviations: BMI, body mass index; SD, standard deviation.
a
Chi-square test.
b
t test.
c
1.0 Brazilian real = 0.63000 US dollar.
d
Mann-Whitney test.