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January 2022 (vol. 226, no. 1, pages 28 and 31)

        Ananth CV, Brandt MD. A principled approach to mediation analysis in perinatal epidemiology. Am J Obstet Gynecol 2022;226:24-32.e6.
        In the Expert Review article cited above, the headings of columns 4 and 5, “Natural direct effect” and “Natural indirect effect,” were transposed in Table 4, “Association between placental abruption and risk of perinatal mortality: mediation effects by preterm delivery (<37 weeks’ gestation; binary mediator) and gestational age (continuous mediator): Collaborative Perinatal Project, 1959 to 1966” (page 31).
        Two citations of the table on the same page of text accordingly require revision. The first (page 28, column 2, under the subheading “Interpretation of Causal Parameters,” sentence 3) should read: “The RRs of TE, NDE, and NIE were 11.30 (95% CI, 9.84–12.73), 1.86 (95% CI, 1.67–2.09), and 6.07 (95% CI, 5.15–7.22), respectively, for the causal effect of abruption on perinatal mortality, adjusted for several confounders (Table 4)” (TE, total causal effect; NDE, natural direct effect; NIE, natural indirect effect). The sentence previously read: “The RRs of TE, NDE, and NIE were 11.30 (95% CI, 9.84–12.73), 6.07 (95% CI, 5.15–7.22), and 1.86 (95% CI, 1.67–2.09), respectively, for the causal effect of abruption on perinatal mortality, adjusted for several confounders (Table 4).”
        The second citation of the table (page 28, column 3, first full paragraph, sentence 2) should read: “The analysis indicates that the RRs for the NIE and NDE were 6.59 (95% CI, 5.53–7.94) and 1.58 (95% CI, 1.49–1.69), respectively (Table 4).” The sentence previously reversed the order of “NIE” and “NDE.”
        These corrections have been made in the online version of the article at ajog.org.

        Linked Article

        • A principled approach to mediation analysis in perinatal epidemiology
          American Journal of Obstetrics & GynecologyVol. 226Issue 1
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            For many research questions in perinatal epidemiology, gestational age is a mediator that features the causal pathway between exposure and outcome. A mediator is an intermediate variable between an exposure and outcome, which is influenced by the exposure on the causal pathway to the outcome. Therefore, conventional analyses that adjust, stratify, or match for gestational age or its proxy (eg, preterm vs term deliveries) are problematic. This practice, which is entrenched in perinatal research, induces an overadjustment bias.
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