Mass Deworming for Soil-Transmitted Helminths and Schistosomiasis among Pregnant Women: A Systematic Review and Individual Participant Data Meta-Analysis

Abstract

Background: Soil transmitted helminthiasis (STH) and schistosomiasis during pregnancy can cause active and debilitating disease with adverse birth outcomes. A recent estimation suggests that approximately 688 million girls and women of reproductive age (WRA) are at risk of helminth infections; including 140 million pregnant and lactating women and another 108 million adolescent girls. Mass deworming is regarded as the most effective means of controlling morbidity and mortality with STH and schistosomiasis; however there are various factors that could potentially modify its effectiveness including baseline nutritional status, worm burden and concomitant interventions. Currently, it is difficult to establish whether mass deworming during pregnancy has beneficial effects under certain conditions and limited effects under others. Objectives: 1. To conduct a systematic review and meta-analysis on the impact of deworming during pregnancy. 2. To conduct a systematic review and meta-analysis on the impact of interventions other than deworming; including water, sanitation and hygiene (WASH) interventions. 3. To conduct an individual participants data (IPD) meta-analysis to identify the factors that explain variation in the effect estimates of mass deworming. 4. To discuss the current guidelines on mass deworming, the challenges and the economic perspective of mass deworming for WRA. Methods: To achieve the aforementioned objectives, following methodology was adopted: 1. A systematic review and meta-analysis evaluating the effectiveness of mass deworming during pregnancy. 2. A systematic review and meta-analysis evaluating the effectiveness of WASH interventions during pregnancy. 3. An IPD meta-analysis to explore whether the effect of mass deworming during pregnancy varies with individual characteristics, intensity of infection, socioeconomic status, sanitation environment and co-interventions. Results: 1. Findings from the systematic review assessing mass deworming during pregnancy suggest that it does not have any impact on maternal anaemia; however it significantly reduced the prevalence of STH and schistosomiasis. There was no impact of mass deworming during pregnancy on haemoglobin, birth weight, low birth weight (LBW), preterm birth, perinatal mortality, stillbirths, neonatal mortality and congenital abnormalities. 2. Findings from the systematic review on interventions other than mass deworming among pregnant women and WRA suggest that the data are too scarce and of low quality to inform best practice. 3. The IPD component of the thesis captured majority of the existing data (70% of the total potential participant population). 4. Findings from the IPD analysis suggest that mass deworming during pregnancy is associated with reducing anaemia with no apparent impact on infection intensity, LBW and preterm birth. These analyses were limited by the availability of data for the impact by subgroups and effect modification. Further studies accounting for maternal baseline worm intensities, concomitant iron/folic acid supplementation and antenatal care coverage could change these findings. Conclusion Mass deworming remains the recommended strategy to prevent and treat STH and schistosomiasis; however deworming alone is insufficient to achieve improvements in all maternal and newborn health outcomes. It is essential to address other factors such as poor sanitation, food insecurity and malnutrition. There is a need to support and promote open data policy for future IPDs to test new hypothesis.