Antenatal epidemiological risk factors such as parental asthma, maternal smoking and the number of older siblings have been shown to be associated with the risks of atopy and asthma in children. Using cord blood mononuclear cells (CBMCs) obtained at birth, a decreased production of Th1-associated cytokines, such as IFN-γ and IL-12, has been reported in newborn infants who subsequently develop allergy and atopy. Th1/Th2 balance may thus be biased towards Th2 already at birth in children later developing allergic diseases.