Twins suffer a disproportionately higher burden of adverse perinatal outcomes than singletons. However, the degree to which preterm delivery shapes the relationship between abruption and perinatal mortality in twins is unknown. Through causal mediation decomposition, we examine how preterm delivery mediates the effect of abruption on perinatal mortality among twins using the US-matched multiple birth data (1995–2000). We estimated the hazard ratio (HR) from Cox models with gestational age as the timescale. We decomposed the total effect (TE) into counterfactual natural direct (NDE) and natural indirect (NIE) effects. 557,220 matched twin births, 1.3% (n = 7032) resulted in abruption with higher perinatal mortality rates than non-abruption births (143 versus 36 per 1000 births, respectively) and a 4.53-fold (95% confidence interval [CI]: 4.23, 4.82) increased hazard of perinatal mortality. HRs for NDE and NIE were 3.05 (95% CI: 2.84, 3.24) and 1.49 (95% CI: 1.49, 1.47, 1.50), respectively, and the proportion mediated (PM) was 41%. PM increased as the gestational age at delivery decreased. Associations persisted after correction for unmeasured confounders. The best strategies to improve perinatal delivery are delivery when abruption complicates twin pregnancies at term gestations and expectant management (avoiding early preterm delivery), if feasible, when abruption complicates twin pregnancies at preterm gestations.

双胞胎遭受的不良围产期结局负担比单胎不成比例地高。然而，早产在多大程度上影响了双胞胎早剥与围生儿死亡率之间的关系尚不清楚。通过因果中介分解，我们使用美国匹配的多胞胎数据 （1995-2000） 研究了早产如何介导早剥对双胞胎围产期死亡率的影响。我们以胎龄为时间尺度估计了 Cox 模型的风险比 （HR）。我们将总效应 （TE） 分解为反事实自然直接 （NDE） 和自然间接 （NIE） 效应。557,220 例匹配的双胞胎婴儿，1.3% （n = 7032） 导致胎盘早剥，围生儿死亡率高于非早剥婴儿（分别为每 1000 名新生儿 143 例和 36 例），围生儿死亡风险增加 4.53 倍 （95% 置信区间 [CI]： 4.23， 4.82）。NDE 和 NIE 的 HR 分别为 3.05 （95% CI： 2.84， 3.24） 和 1.49 （95% CI： 1.49， 1.47， 1.50），介导比例 （PM） 为 41%。PM 随着分娩时胎龄的降低而增加。对于未测量的混杂因素，在校正后，关联仍然存在。改善围产期分娩的最佳策略是在足月妊娠时胎盘早剥使双胎妊娠复杂化时分娩，如果可行，当早剥使早胎妊娠复杂化时，进行期待处理（避免早期早产）。