Cox PH shared frailty models for the association between IPV and time-to-pregnancy for all incident pregnancies (n=90 446 women; 52 959 pregnancies; 232 394 person-years), and for IPV and time-to-unintended pregnancy for pregnancies that resulted in live births (n=92 848 women; 13 541 unintended pregnancies; 310 319 person-years)
| Shared frailty Cox PH for all incident pregnancies* | Shared frailty Cox PH for unintended pregnancies that resulted in live births* | |
| Participant-level, time-varying variables | HR (95% CI) | HR (95% CI) |
| Intimate partner violence† | 1.51 (1.38 to 1.66) | 1.30 (1.25 to 1.34) |
| Intimate partner violence × ln(time)‡ | 0.89 (0.86 to 0.92) | |
| Number of surviving boys/total surviving children | 0.93 (0.91 to 0.95) | 0.99 (0.95 to 1.03) |
| Variance of the country-level frailty (SE) | 0.09 (0.02) | 0.34 (0.09) |
*Includes an interaction between a restricted cubic spline with two knots for time and age (modelled as a restricted cubic spline with two knots), marital status, maternal education, partner’s education, household wealth quintile and rural residence, conditional on country-level frailty terms.
†Includes emotional, physical and/or sexual violence.
‡IPV-time dependency not included in Cox PH models for time-to-unintended pregnancy.
IPV, intimate partner violence; PH, proportional hazards.