In this population-based study, a strong tendency to repeat small-for-gestational age (SGA) deliveries in successive births has been documented. Mothers who showed this tendency ('repeater mothers') differed from mothers who had only one SGA delivery in their first three single births. In the group of mothers with only one SGA birth, there was an association between the SGA birth and such pregnancy complications as preeclampsia, vaginal bleeding, and placental pathologies. No similar association with medical complications during pregnancy was found for the repeater mothers. Instead, these mothers were characterized by lower educational attainment and lower socio-economic status based on husbands' occupational groupings. Thus, the tendency to repeat SGA birth appears to be mediated in part through more adverse living conditions and lifestyle habits.