Environmental risk factors for childhood insulin-dependent diabetes mellitus (IDDM) have been investigated using data abstracted from the obstetric records of mothers participating in a population-based case-control study of children (0-15 years) diagnosed with IDDM during 1993-1994. A univariate analysis of 196 age and sex matched sets (129 triplets, 67 pairs) gave significantly raised odds ratios (OR) for mothers over 35 years (OR 2.13, 95%CI 1.04-4.36) and the following exposures in pregnancy: amniocentesis (3.85, 1.34-11.04), oedema, proteinuria and/or hypertensive disorders (1.62, 1.03-2.54), excessive weight gain (7.12, 1.50-33.79) and complications in labour (1.49, 1.00-2.21). The risk previously associated with caesarean deliveries was confirmed and the trend of increasing risk with age was significant. Adjusting separately for mothers with IDDM (4 cases, 0 control subjects), parity and small for gestational age failed to have any influence on the pregnancy risk factors or caesarean delivery. Case mothers undergoing amniocentesis were significantly younger compared to their control counterparts (p = 0.02) and the majority were given the test to determine fetal maturity, late in pregnancy, rather than to identify chromosomal abnormalities. Oedema, proteinuria and/or hypertension conferred an increased risk throughout pregnancy, particularly in the first two trimesters. No specific pattern of risk was present for any age group. Multivariate modelling of the significant OR, using conditional logistic regression, retained excessive weight gain as significant. The overall results present a risk profile of older mothers whose babies may be exposed to adverse intrauterine conditions and delivery by caesarean section.