Epidemiological studies have shown that pregnant women continue to take substantial quantities of drugs, particularly those readily available to them without prescription. Little is known of the attitudes and knowledge among pregnant women of the effects of these substances on the fetus. Awareness of the effects on the fetus of commonly used drugs, cigarettes and alcohol among 514 women in the postnatal wards of two maternity units in Glasgow was assessed by self completion questionnaire between October 1987 and April 1988. Most of the women recognised that the fetus is most at risk of being harmed by drugs during the first 3 months of pregnancy. The majority felt it was safest not to smoke cigarettes and were aware of the adverse effects of smoking on fetal growth. Over half thought smoking was harmful while breastfeeding. Over half thought that alcohol should be avoided altogether in pregnancy and that drinking could harm the fetus. Most women considered alcohol harmful to the breast feeding baby. The majority of the women would opt for paracetamol containing analgesics only and only a small proportion would take one containing aspirin. Only half the study population would take a prescribed antibiotic. A generally high level of awareness of commonly used drugs was demonstrated although there are areas where further health education could be directed. The study has highlighted areas worthy of further research.