Mean TTP Unadjusted model Unadjusted model Adjusted modela Adjusted modela
Characteristics FOR 95% CI FOR 95% CI
Age, years (women) (%)b Age, years (women) (%)b Age, years (women) (%)b Age, years (women) (%)b Age, years (women) (%)b Age, years (women) (%)b Age, years (women) (%)b
20–24 15.5 ref ref ref ref
25–29 14.6 0.89 0.84–0.95 0.82 0.74–0.92
30–34 16.7 0.92 0.83–1.02 0.85 0.71–1.01
35–39 35.5 0.39 0.34–0.45 0.44 0.36–0.55
≥40 18.0 0.67 0.48–0.95 0.40 0.24–0.69
P value <.001 <.001 <.001 <.001
Education (women) (%) Education (women) (%) Education (women) (%) Education (women) (%) Education (women) (%) Education (women) (%) Education (women) (%)
Primary school and below 24.3 ref ref ref ref
Middle school 17.5 1.25 1.12–1.41 1.02 0.87–1.20
High school 15.8 1.29 1.13–1.47 1.12 0.92–1.36
College and beyond 14.8 1.25 1.10–1.43 1.31 1.04–1.64
P value .001 .001 .036 .036
Employment (women) (%) Employment (women) (%) Employment (women) (%) Employment (women) (%) Employment (women) (%) Employment (women) (%) Employment (women) (%)
Employmentc 19.0 ref ref ref ref
Unemployment 14.2 1.57 1.48–1.65 1.60 1.48–1.73
P value <.001 <.001 <.001 <.001
Annual household income, yuan (%) Annual household income, yuan (%) Annual household income, yuan (%) Annual household income, yuan (%) Annual household income, yuan (%) Annual household income, yuan (%) Annual household income, yuan (%)
<10,000 16.7 ref ref ref ref
10,000–19,999 16.9 0.95 0.89–1.01 0.97 0.89–1.06
>20,000 19.4 0.79 0.73–0.85 0.75 0.67–0.84
P value <.001 <.001 <.001 <.001
Age, years (men) (%)b Age, years (men) (%)b Age, years (men) (%)b Age, years (men) (%)b Age, years (men) (%)b Age, years (men) (%)b Age, years (men) (%)b
20–24 15.3 ref ref ref ref
25–29 14.5 0.95 0.88–1.03 0.93 0.84–1.04
30–34 14.9 1.00 0.91–1.10 0.85 0.73–0.99
35–39 32.0 0.50 0.44–0.56 0.55 0.46–0.66
≥40 19.4 0.67 0.53–0.83 0.76 0.54–1.07
P value <.001 <.001 <.001 <.001
Education (men) (%) Education (men) (%) Education (men) (%) Education (men) (%) Education (men) (%) Education (men) (%) Education (men) (%)
Primary school and below 24.0 ref ref ref ref
Middle school 17.5 1.31 1.15–1.50 1.05 0.87–1.27
High school 15.7 1.42 1.23–1.64 1.24 1.01–1.53
College and beyond 15.3 1.31 1.13–1.52 1.15 0.90–1.46
P value <.001 <.001 .034 .034
Toxic exposure (men)d Toxic exposure (men)d Toxic exposure (men)d Toxic exposure (men)d Toxic exposure (men)d Toxic exposure (men)d Toxic exposure (men)d
No 17.1 ref ref ref ref
Yes 20.9 0.73 0.62–0.85 0.67 0.54–0.84
P value <.001 <.001 <.001 <.001
Duration of cohabitation, yearse Duration of cohabitation, yearse 1.00 0.99–1.00 1.06 1.05–1.07
Menstrual cycle interval (day) Menstrual cycle interval (day) Menstrual cycle interval (day) Menstrual cycle interval (day) Menstrual cycle interval (day) Menstrual cycle interval (day) Menstrual cycle interval (day)
≤23 16.0 0.81 0.73–0.90 0.88 0.75–1.03
24–35 18.0 ref ref ref ref
>35 32.1 0.42 0.36–0.50 0.49 0.40–0.61
P value <.001 <.001 <.001 <.001
History of abnormal pregnancy History of abnormal pregnancy History of abnormal pregnancy History of abnormal pregnancy History of abnormal pregnancy History of abnormal pregnancy History of abnormal pregnancy
No 16.8 ref ref ref ref
Yes 20.7 0.77 0.71–0.84 0.83 0.74–0.94
P value <.001 <.001 .003 .003
Parity Parity Parity Parity Parity Parity Parity
Nullipara 17.7 ref ref ref ref
Multipara 16.1 1.08 1.02–1.14 1.13 1.02–1.25
P value .010 .010 .022 .022