Table 3

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 variablesHR (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 children0.93 (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.