Association between pregnancy affected by vaginal bleeding and women's mortality – a Danish cohort study

Abstract

We aimed to investigate the association between vaginal bleeding (VB) in pregnancy and women’s mortality, using VB-unaffected pregnancies, terminations and miscarriages as comparators. This was an observational cohort study using nationwide registries of Denmark linked at an individual level. Population or Sample 1 354 181 women and their 3 162 317 pregnancies (1979–2017), including 70 835 VB-affected pregnancies and comparators, i.e. 2 236 359 VB-unaffected pregnancies ending in childbirth, 589 697 terminations, and 265 426 miscarriages. We followed pregnancies until the earliest date of woman’s death, emigration or end of data. Main outcome measures All-cause and cause-specific mortality rates per 10 000 person-years (PY) and hazard ratios (HRs) with 95% confidence intervals (CIs) adjusted using Cox proportional hazards regression for age, calendar year, pre-existing chronic conditions and socio-economic factors. Results There were 2320 deaths from any cause among women following VB-affected pregnancy (mortality rate 15.2, 95% CI 14.6–15.9 per 10 000 PY), 55 030 deaths following VB-unaffected pregnancy (mortality rate 12.7, 95% CI 12.6–12.8), 27 500 deaths following a termination (mortality rate 21.9, 95% CI 21.6–22.1), and 10 865 deaths following a miscarriage (mortality rate 19.2, 95% CI 18.8–19.6). For comparison of VB-affected versus VB-unaffected pregnancies, associations with all-cause (HR 1.14, 95% CI 1.09–1.19), natural causes (HR 1.15, 95% CI 1.09–1.22) and non-natural causes (HR 1.27, 95% CI 1.08–1.48) mortality were attenuated in a sensitivity analysis of pregnancies recorded in 1994–2017 (HR 1.00, 95% CI 0.90–1.12, HR 0.98, 95% CI 0.85–1.14 and HR 1.04, 95% CI 0.72–1.51, respectively). Contrasts with remaining comparators did not suggest increased risks of all-cause, natural or non-natural mortality causes. Conclusion - We found no evidence of an increased risk of women’s mortality following VB-affected versus VB-unaffected pregnancy, termination or miscarriage.