OBJECTIVES: To identify lifestyle factors associated with subfertility (time to pregnancy >12 months) among women attending an antenatal clinic, and to determine whether this changed from 2001 to 2007. METHODS: Waiting-room surveys administered in 2001 and 2007. RESULTS: There were significant changes in lifestyle factors between 2001 and 2007, including such factors as previous contraceptive use and obesity, smoking, alcohol and caffeine intake of both partners. All changes were in the direction favourable to health and fertility. However, despite these health improvements, there was no overall decrease in the prevalence of subfertility in the antenatal population. Mathematical modelling showed that even if the entire population had improved their lifestyle this would have made little difference to the proportion of subfertile couples. CONCLUSIONS: A modest improvement in lifestyle over a period of 6 years in couples trying to conceive a pregnancy did not lead to any reduction in the incidence of subfertility and even substantial changes would not have made a significant difference.