Objective: To determine whether the excess aluminum sulphate accidentally added to the local water supply in north Cornwall in July 1988 had an adverse effect on the outcome of pregnancies.
Design: Outcomes of all singleton pregnancies in the affected area at the time of the incident (n = 92) were compared with those in two control groups: pregnancies in this area completed before the incident (n = 68) and pregnancies in a neighbouring area (n = 193).
Subjects: Mothers in the three groups, among whom there were 13 miscarriages, five terminations of pregnancy, and 336 live births.
Main outcome measures: Fetal and perinatal loss, birth weight, gestation, obstetric complications, neonatal condition, and congenital defects.
Results: Among 88 pregnancies in women exposed to excess aluminum sulphate there was no excess of perinatal deaths (n = 0), low birthweight (n = 3), preterm delivery (n = 4), or severe congenital malformations (n = 0). There was, however, an increased rate of talipes in exposed fetuses (four cases, one control; p = 0.01).
Conclusions: Because of small numbers it is not possible to say that high doses of aluminum sulphate are safe in pregnancy, but there is no evidence from this study of major problems apparent at birth.