Background: Worms may protect against allergy. Early-life worm exposure may becritical, but this has not been fully investigated.Objectives: To investigate whether worms in pregnancy and in early childhood areassociated with childhood eczema incidence. Methods: The Entebbe Mother and Baby Study, an anthelminthic treatment trial,enrolled pregnant women between 2003 and 2005 in Uganda. Mothers were investigatedfor worms during pregnancy and children annually. Eczema was doctor-diagnosed frombirth to age five years. A planned observational analysis was conducted within the trialcohort to investigate associations between worms and eczema. Results: Data for 2345 live-born children were analysed. Hookworm was the mostprevalent maternal worm (45%). Childhood worms were less prevalent. Eczemaincidence was 4.68/100 person-years. Maternal hookworm was associated withreduced eczema incidence [adjusted hazard ratio (95% confidence interval), p-value:0.71(0.51–0.99), 0.04] and modified effects of known risk factors for eczema:Dermatophagoides-specific IgE in children was positively associated with eczemaincidence if the mother had no hookworm [2.72(1.11–6.63), 0.03], but not if the motherhad hookworm [0.41(0.10–1.69), 0.22], interaction p-value = 0.03. Similar interactionswere seen for maternal history of eczema {[2.87(1.31–6.27, 0.008) vs. [0.73(0.23–2.30),0.60], interaction p-value = 0.05}, female gender {[1.82(1.22–2.73), 0.004 vs. [0.96(0.60–1.53), 0.87], interaction p-value = 0.04} and allergen-specific IgE. ChildhoodTrichuris trichiura and hookworm were inversely associated with eczema. Conclusions: Maternal hookworm modifies effects of known risk factors for eczema.Mechanisms by which early-life worm exposures influence allergy need investigation.Worms or worm products, and intervention during pregnancy have potential forprimary prevention of allergy.