Background Prenatal antioxidant supplementation might influence fetal lung growth and development and reduce infant respiratory morbidity. The aim of this study was to test the hypothesis that infants of mothers at risk of pre-eclampsia who were randomised to receive high-dose vitamins C and E (1000 mg vitamin C and 400 IU RRR α-tocopherol daily) during pregnancy would have better respiratory outcomes than infants whose mothers were randomised to receive placebo.

Methods Respiratory outcomes to 2 years of age were documented using questionnaires and, in a subset, by recording their healthcare utilisation and calculating the cost of care data.

Results 330 women who had taken vitamin supplementation and 313 who had taken placebo completed the respiratory questionnaire (386 and 366 infants, respectively). There were no significant differences between the two groups in the proportions diagnosed with asthma. 54 women who had taken vitamin supplementation and 45 who had taken placebo took part in the healthcare utilisation study (65 and 53 infants, respectively). On average, infants of mothers receiving vitamin supplementation had 2.6 (99% CI 0.8 to 5.1) times more A&E/outpatient visits and 3.2 (99% CI 0.2 to 6.9) times more GP visits than infants of mothers receiving placebo, and their costs of care were £226 (99% CI £27 to £488) more for outpatient admissions, £57 (99% CI £3 to £123) more for GP visits and £22 (99% CI £3 to £50) more for medications.

Conclusions High-dose antenatal vitamin C and E supplementation does not improve infant respiratory outcome and is associated with increased healthcare utilisation and cost of care.