Table 3.
Estimated reduction in rates of PND symptoms achieved by intervention on the preconception exposure (TCE) and antenatal mediators (IIE), in women with persistent preconception symptoms (N = 600 pregnancies).
| PNDa symptoms two months postpartum |
PNDa symptoms one year postpartum |
|||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| risk reduction (%) | 95% CI | p-value | proportion of TCE (%) | risk remaining in exposed (%) | risk reduction (%) | 95% CI | p-value | proportion of TCE (%) | risk remaining in exposed (%) | |
| risk of PND symptoms under exposure (no intervention) | — | — | — | — | 15.0 | — | — | — | — | 16.2 |
| total causal effect of the preconception exposure (TCE)b | 11.8 | 4.5, 19.0 | 0.002 | 100 | 3.2 | 13.5 | 5.9, 21.1 | 0.000 | 100 | 2.7 |
| estimated effects of hypothetical intervention on the mediators | ||||||||||
| Scenario 1: best-case intervention eliminating all mediator risk | ||||||||||
| interventional indirect effects via mediators (IIE)c | ||||||||||
| IIE1 (antenatal low social support) | 3.0 | −0.3, 6.3 | 0.073 | 26 | 12.0 | 1.5 | −1.8, 4.7 | 0.376 | 11 | 14.7 |
| IIE2 (antenatal depressive symptoms) | 4.9 | 1.0, 8.8 | 0.015 | 42 | 10.1 | 6.3 | 2.2, 10.4 | 0.003 | 47 | 9.9 |
| IIE3 (antenatal low maternal–fetal attachment) | 1.3 | −1.2, 3.9 | 0.304 | 11 | 13.7 | <1 | −3.0, 1.7 | 0.601 | −5 | 16.8 |
| IIE4 (antenatal low income) | 1.9 | −0.6, 4.3 | 0.130 | 16 | 13.1 | <1 | −1.1, 2.9 | 0.380 | 7 | 15.3 |
| IIEint (mediators' interdependence) | −2.1 | −4.4, 0.2 | 0.073 | −18 | — | <1 | −2.7, 1.6 | 0.625 | −4 | — |
| interventional direct effect not via mediators (IDE)d | 2.7 | −2.9, 8.4 | 0.341 | 23 | — | 6.0 | −1.2, 13.3 | 0.104 | 45 | — |
| Scenario 2: pragmatic intervention lowering mediator levels to those in the unexposed | ||||||||||
| interventional indirect effects via mediators (IIE)e | ||||||||||
| IIE1 (antenatal low social support) | 2.3 | −0.4, 5.0 | 0.094 | 20 | 12.7 | 1.1 | −1.5, 3.8 | 0.394 | 8 | 15.1 |
| IIE2 (antenatal depressive symptoms) | 3.9 | 0.5, 7.3 | 0.025 | 33 | 11.1 | 4.7 | 1.2, 8.3 | 0.009 | 35 | 11.5 |
| IIE3 (antenatal low maternal–fetal attachment) | <1 | −1.2, 1.3 | 0.934 | <1 | 14.9 | <1 | −1, 0.8 | 0.883 | <1 | 16.3 |
| IIE4 (antenatal low income) | <1 | −1.3, 2.1 | 0.638 | 4 | 14.6 | <1 | −0.9, 1.2 | 0.805 | 1 | 16.1 |
| IIEint (mediators' interdependence) | −1.0 | −2.6, 0.6 | 0.217 | –9 | — | <1 | −2, 1.2 | 0.653 | −3 | — |
| interventional direct effect not via mediators (IDE)f | 6.1 | 0.2, 19.0 | 0.002 | 52 | — | 7.9 | 1.1, 14.7 | 0.023 | 59 | — |
aPND, postnatal depression. All models adjusted for mother's family of origin, adolescent and young adult preconception and periconceptional characteristics.
bRisk difference comparing exposed versus unexposed.
cSet given mediator under exposure to zero (no risk).
dRisk difference comparing exposed versus unexposed under intervention setting all mediators to zero (no risk).
eSet given mediator under exposure to a random draw from its distribution under no exposure.
fRisk difference comparing exposed versus unexposed under intervention jointly lowering all mediators to those in unexposed.