In mothers who suffer from helminth infections or allergic diseases, prenatal sensitization with antigens/allergens is suspected to bias the immune system of the offspring towards a Th2-type response. To investigate this at the antibody level, we collected 113 blood samples on filter paper from a paediatric population aged 3 months to 10 years and their mothers, who resided in an area endemic for brugian filariasis in Indonesia. The results showed that antibody levels in children were strongly correlated with maternal antibody levels. However, for anti-filarial IgG4 and IgE this relationship was manifested directly after birth, whereas for total antibody levels a positive correlation could be detected only with children aged > or = 2 years. To investigate the influence of paternal antibody on progeny, specific IgG4 was determined in a different set of samples from 229 children and both of their parents. Interestingly, the influence of paternal IgG4 became apparent only after the age of 4 years. In contrast, maternal antibody levels were already correlated to levels produced by their offspring at a young age (3 months onwards). Taken together, it appears that children can become sensitized to parasite antigens in utero, allowing them to produce Th2-dependent specific IgG4 and IgE antibodies at a young age, whereas with increasing age, the influence of environmental factors, shared in households, such as filarial transmission and other helminth infections, becomes dominant.