Abstract. The impact of insecticide (permethrin)-treated bed nets (ITNs) on malaria in pregnancy was studied in a rural area in western Kenya with intense perennial malaria transmission. All households in 40 of 79 villages were randomized to receive ITNs by January 1997. The ITNs were distributed in control villages two years later. Complete data on birth outcome were available on 2,754 (89.6%) of 3,072 deliveries. Women (n ‫ס‬ 780) were followed monthly throughout pregnancy in 19 of 79 villages. Among gravidae 1-4, ITNs were associated with reductions of 38% (95% confidence interval [CI] ‫ס‬ 17-54%) in the incidence of malaria parasitemia and 47% (95% CI ‫ס‬ 6-71%) in the incidence of severe malarial anemia (hemoglobin level < 8 g/dL with parasitemia) during pregnancy. At the time of delivery, mean hemoglobin levels were 0.6 g/dL (95% CI ‫ס‬ 0.01-1.2 g/dL) higher, the prevalence of placental or maternal malaria was reduced by 35% (95% CI ‫ס‬ 20-47%), and the prevalence of low birth weight was reduced by 28% (95% CI ‫ס‬ 2-47%) in gravidae 1-4 from ITN villages. No beneficial impact was observed in gravidae five or higher. In areas of intense perennial malaria transmission, permethrin-treated bed nets reduce the adverse effect of malaria during the first four pregnancies.

Information on the impact of insecticide (permethrin)-treated bed nets (ITNs) from randomized controlled trials in areas of intense perennial malaria transmission is limited. As part of a large-scale, community-based, group-randomized controlled trial of the effect of ITNs on childhood mortality in a holoendemic area in western Kenya, we conducted three cross-sectional surveys in 60 villages to assess the impact of ITNs on morbidity in 1,890 children less than three years old. Children in ITN and control villages were comparable pre-intervention, but after the introduction of ITNs, children in intervention villages were less likely to have recently experienced illness requiring treatment (protective efficacy [95% confidence intervals] ‫ס‬ 15% [1−26%]), have an enlarged spleen (32% [20−43%]), be parasitemic (19% [11−27%]), have clinical malaria (44% [6−66%]), have moderately severe anemia (hemoglobin level < 7.0 g/dL; 39% [18−54%]), or have a pruritic body rash, presumably from reduced nuisance insect bites (38% [24−50%]). Use of ITNs was also associated with significantly higher mean weight-forage Z-scores and mid-upper arm circumferences. There was no evidence, however, that ITNs reduced the risk of helminth infections, diarrhea, or upper or lower respiratory tract infections. The ITNs substantially reduced malaria-associated morbidity and improved weight gain in young children in this area of intense perennial malaria transmission.

Background Owing to increasing sulfadoxine-pyrimethamine (SP) resistance in sub-Saharan Africa, monitoring the effectiveness of intermittent preventive therapy in pregnancy (IPTp) with SP is crucial. Methods Between 2009 and 2013, both the efficacy of IPTp-SP at clearing existing peripheral malaria infections and the effectiveness of IPTp-SP at reducing low birth weight (LBW) were assessed among human immunodeficiency virus–uninfected participants in 8 sites in 6 countries. Sites were classified as high, medium, or low resistance after measuring parasite mutations conferring SP resistance. An individual-level prospective pooled analysis was conducted. Results Among 1222 parasitemic pregnant women, overall polymerase chain reaction–uncorrected and –corrected failure rates by day 42 were 21.3% and 10.0%, respectively (39.7% and 21.1% in high-resistance areas; 4.9% and 1.1% in low-resistance areas). Median time to recurrence decreased with increasing prevalence of Pfdhps-K540E. Among 6099 women at delivery, IPTp-SP was associated with a 22% reduction in the risk of LBW (prevalence ratio [PR], 0.78; 95% confidence interval [CI], .69–.88; P < .001). This association was not modified by insecticide-treated net use or gravidity, and remained significant in areas with high SP resistance (PR, 0.81; 95% CI, .67–.97; P = .02). Conclusions The efficacy of SP to clear peripheral parasites and prevent new infections during pregnancy is compromised in areas with >90% prevalence of Pfdhps-K540E. Nevertheless, in these high-resistance areas, IPTp-SP use remains associated with increases in birth weight and maternal hemoglobin. The effectiveness of IPTp in eastern and southern Africa is threatened by further increases in SP resistance and reinforces the need to evaluate alternative drugs and strategies for the control of malaria in pregnancy.