BACKGROUND: Although schizotypal traits, such as anhedonia and aberrant perceptions, may increase the risk for schizophrenia-spectrum disorders, little is known about early-life characteristics that predict more pronounced schizotypal traits. AIMS: To examine whether birth size or several other early-life factors that have been previously linked with schizophrenia predict schizotypal traits in adulthood. METHOD: Participants of the Northern Finland 1966 Birth Cohort Study (n = 4976) completed a questionnaire on positive and negative schizotypal traits at the age of 31 years. RESULTS: Lower placental weight, lower birth weight and smaller head circumference at 12 months predicted elevated positive schizotypal traits in women after adjusting for several confounders (P<0.02). Moreover, higher gestational age, lower childhood family socioeconomic status, undesirability of pregnancy, winter/autumn birth, higher birth order and maternal smoking during pregnancy predicted some augmented schizotypal traits in women, some in men and some in both genders. CONCLUSIONS: The results point to similarities in the aetiology of schitzotypal traits and schizophrenia-spectrum disorders.