The World Health Organization has identified substance use in the top 20 risk factors for ill health. Risks in pregnancy are compounded, with risk to the woman's health, to pregnancy progression and on both the foetus and the newborn. Intrauterine exposure can result in negative influences on offspring development, sometimes into adulthood. With effectively two patients, there is a clear need for antenatal screening. Biomarker reliability is limited and research efforts have been directed to self-report tools, often attempting to address potential lack of veracity if women feel guilty about substance use and worried about possible stigmatization. Tools, which assume the behaviour, are likely to elicit more honest responses; querying pre-pregnancy use would likely have the same effect. Although veracity is heightened if substance use questions are embedded within health and social functioning questionnaires, such tools may be too lengthy clinically. It has been proposed that screening only for alcohol and tobacco, with focus on the month pre-pregnancy, could enable identification of all other substances. Alternatively, the Revised Fagerstrom Questionnaire could be used initially, tobacco being highly indicative of substance use generally. The ASSIST V.3.0 is readily administered and covers all substances, although the pregnancy ‘risk level’ cut-off for tobacco is not established. Alcohol tools – the 4Ps, TLFB and ‘drug’ CAGE (with E: query of use to avoid withdrawal) – have been studied with other substances and could be used. General psychosocial distress and mental ill-health often co-exist with substance use and identification of substance use needs to become legitimate practice for obstetric clinicians.