A quasi-experimental study estimating the impact of long-lasting insecticidal nets with and without piperonyl butoxide on pregnancy outcomes

• Published in: Malaria Journal
• Main Authors: Michelle E. Roh, Brenda Oundo, Grant Dorsey, Stephen Shiboski, Roly Gosling, M. Maria Glymour, Sarah G. Staedke, Adam Bennett, Hugh Sturrock, Arthur Mpimbaza
• Format: Article in Journal/Newspaper
• Language: English
• Published: BMC 2022
• Subjects: Plasmodium falciparum; Malaria in pregnancy; Long-lasting insecticidal net; Low birthweight; Stillbirth; Difference-in-differences; Arctic medicine. Tropical medicine; RC955-962; Infectious and parasitic diseases; RC109-216; Arctic
• Online Access: https://doi.org/10.1186/s12936-021-04034-0; https://doaj.org/article/429a11dd7c6d47d5b2a53594e8709c12

Abstract Background Long-lasting insecticidal nets (LLINs) are the main vector control tool for pregnant women, but their efficacy may be compromised, in part, due to pyrethroid resistance. In 2017, the Ugandan Ministry of Health embedded a cluster randomized controlled trial into the national LLIN campaign, where a random subset of health subdistricts (HSDs) received LLINs treated with piperonyl butoxide (PBO), a chemical synergist known to partially restore pyrethroid sensitivity. Using data from a small, non-randomly selected subset of HSDs, this secondary analysis used quasi-experimental methods to quantify the overall impact of the LLIN campaign on pregnancy outcomes. In an exploratory analysis, differences between PBO and conventional (non-PBO) LLINs on pregnancy outcomes were assessed. Methods Birth registry data (n = 39,085) were retrospectively collected from 21 health facilities across 12 HSDs, 29 months before and 9 months after the LLIN campaign (from 2015 to 2018). Of the 12 HSDs, six received conventional LLINs, five received PBO LLINs, and one received a mix of conventional and PBO LLINs. Interrupted time-series analyses (ITSAs) were used to estimate changes in monthly incidence of stillbirth and low birthweight (LBW; <2500 g) before-and-after the campaign. Poisson regression with robust standard errors modeled campaign effects, adjusting for health facility-level differences, seasonal variation, and time-varying maternal characteristics. Comparisons between PBO and conventional LLINs were estimated using difference-in-differences estimators. Results ITSAs estimated the campaign was associated with a 26% [95% CI: 7–41] reduction in stillbirth incidence (incidence rate ratio (IRR) = 0.74 [0.59–0.93]) and a 15% [-7, 33] reduction in LBW incidence (IRR=0.85 [0.67–1.07]) over a 9-month period. The effect on stillbirth incidence was greatest for women delivering 7–9 months after the campaign (IRR=0.60 [0.41–0.87]) for whom the LLINs would have covered most of their pregnancy. The IRRs estimated from ...