OBJECTIVE: to explore the use of folic acid and other vitamin supplements before and during pregnancy, including type, dosage and form; who recommended supplement use and for what reason; and women's understanding of why they took folic acid. DESIGN: cross-sectional survey. SETTING: a public tertiary referral hospital in Melbourne, Australia. PARTICIPANTS: consecutive pregnant women at 36-38-weeks gestation completed a self-administered survey (available in English, Cantonese, Vietnamese, Turkish and Arabic). MEASUREMENTS: a structured questionnaire was used. Descriptive statistics are presented, with stratified and regression analyses to compare sub-groups. FINDINGS: of 705 eligible women, 588 (83%) agreed to participate. Of these, 88 (15%) completed the questionnaire in a language other than English. Twenty-nine per cent (168/588) of women took pre-pregnancy folic acid supplements. Only 23% reported taking a folic acid supplement for at least 4 weeks before pregnancy. During pregnancy, 79% of women took folic acid, most of whom commenced before 13 weeks. Other vitamin supplements taken during pregnancy were iron (52%), calcium (24%), Vitamin B6 (14%), pregnancy multivitamins (35%) and zinc (7%). Only 8% took no supplements at all in pregnancy. Factors associated with an increased risk of not taking folic acid were income < or =$30,000 (AUD) (adjusted odds ratio (OR) 2.85, 95% CI 1.84, 4.40), smoking during pregnancy (adjusted OR 2.3, 95% CI 1.26, 4.48) and having other than a first baby (adjusted OR 1.89, 95% CI 1.22, 2.93). KEY CONCLUSIONS: uptake of folic acid supplementation in the periconceptional period was well below the target that all women planning pregnancy consume 0.4-0.5mg of folate per day. Less than one-third of this sample took a pre-pregnancy folic acid supplement, with differences in uptake by group. A large proportion of respondents also took a range of other vitamin supplements during pregnancy. IMPLICATIONS FOR PRACTICE: it is important to target women who are less likely to take periconceptional folic acid as well as to increase awareness among women of childbearing age in general.