Table 2 Prevalence of chronic LBP by number of childbirths and pregnancy status
Total number of women in category | Number of women with chronic LBP (%) | PR (95% CI) with adjustment for age only | PR (95% CI) with additional adjustmenta | PR (95% CI) with additional adjustmenta including age at first childbirthb | |
|---|---|---|---|---|---|
Number of women included in the analysis | 28,258 | 25,444 | 21,277 | ||
Number of childbirths | |||||
0 | 3936 | 654 (16.6) | 1.00 (reference) | 1.00 (reference) | |
1 | 3143 | 733 (23.3) | 1.17 (1.06–1.29) | 1.11 (1.01–1.22) | 1.00 (reference) |
2 | 9210 | 2460 (26.7) | 1.18 (1.09–1.29) | 1.12 (1.03–1.22) | 1.02 (0.94–1.10) |
3 | 7147 | 2096 (29.3) | 1.23 (1.13–1.33) | 1.17 (1.07–1.27) | 1.03 (0.95–1.12) |
4 | 2730 | 912 (33.4) | 1.32 (1.20–1.45) | 1.21 (1.10–1.34) | 1.06 (0.96–1.16) |
5 | 958 | 312 (32.6) | 1.25 (1.11–1.41) | 1.11 (0.97–1.27) | 0.96 (0.85–1.09) |
≥ 6 | 539 | 172 (31.9) | 1.21 (1.05–1.40) | 1.07 (0.91–1.27) | 0.91 (0.77–1.07) |
Currently pregnantc | 595 | 80 (13.4) | 0.86 (0.69–1.06) | 0.80 (0.63–1.00) | |
P for categorical effect | < 0.001d | 0.008d | 0.29 | ||
P for linear trend | 0.001b | 0.08b | 0.70 | ||