Objective, To examine for an association between amniotic fluid zinc and pregnancy outcome. Design. A prospective study. Setting. Southmead Hospital, Bristol, UI(. Subjects: 191 amniotic fluid samples from 11 centers in the Southwest of England, obtained at 16-20 weeks gestation. Method: Samples of amniotic fluid (AF) sent for prenatal diagnosis were collected from the laboratory and analysed for zinc level. Data were then collected at a later date concerning pregnancy outcome. Outcome measure: Antenatal complications as well as events in labour, and in particular birth weight and congenital malformations. Results: 182 cases with complete data showed a mean AF zinc level (+/- S.E.) of 1.39 (+/- 0.11). There was no relation between AF zinc and antepartum haemorrhage, pregnancy-induced hypertension, post-partum haemorrhage or time and mode of delivery. Neither was there an association with birth weight. As there were no cases with major malformations, particularly of the central nervous system, possible association could not be ascertained. Conclusion: The study failed to demonstrate any association between AF zinc and abnormal pregnancy outcome. A modified prospective study is suggested to explore this further.