<b>Background: </b>The aetiological factors underlying the worldwide increase in the prevalence of asthma and the international patterns of the prevalence of asthma are not well understood. This has led to consideration of factors such as fetomaternal health which may programme the initial susceptibility to allergic sensitisation, or contribute to the development of asthma independently of sensitisation. <b>Methods: </b>A number of epidemiological studies have examined the relationship between birth anthropometric measures (as a marker of fetomaternal health) and the subsequent development of asthma and atopy in childhood or adult life. <b>Results: </b>Some, but not all of these studies have reported a relationship between enhanced fetal growth and an increased risk of asthma and/or atopy. <b>Conclusion: </b>These findings raise the hypothesis that factors responsible for fetal growth may also lead to programming of the developing respiratory or immune systems, predisposing to the subsequent development of asthma and/or atopy. This hypothesis may explain, in part, the increasing prevalence of asthma and atopy over recent decades, which has occurred concurrently with secular trends for improved fetomaternal health, as measured by anthropometric measurements at birth.