Causal mediation analysis
The causal mediation analysis was performed to disentangle the total
effect of chronic hypertension-perinatal mortality association, with
preterm delivery as the potential mediator (Table 3 ). Much of
the TE of perinatal mortality and its component mortalities was mediated
through preterm delivery. The indirect effect was greatest for perinatal
mortality and stillbirth. Given the strong mediation component of the
chronic hypertension-mortality association that operates through preterm
delivery, the PE estimate is correspondingly high: 87% (95% CI 84,
90).