Fidelity of Interventions to Reduce or Prevent Stress and/or Anxiety from Pregnancy up to Two Years Postpartum: A Systematic Review.

Low levels of intervention fidelity may explain previous inconsistent effects of stress and anxiety reduction interventions. Important methodological areas for improvement include intervention provider training, fidelity of comparator conditions, and consideration of non-specific treatment effects. Increased methodological rigour in fidelity enhancement and assessment will improve intervention implementation and enhance examination of stress and anxiety reduction and prevention interventions delivered during pregnancy and the postpartum.