The report, involving researchers from the Centre for Public Health and the School of Nursing and Midwifery at Queen’s University Belfast and the Belfast Health and Social Care Trust also found, however, that vitamin supplementation could be beneficial in those women with low levels of dietary antioxidants in their blood and that this possibility needs further investigation.
The causes of pre-eclampsia are not known, but it has been suggested that oxidative stress, (where free radicals harm cells), might play a key role in the development of the condition.
In 1999, a small trial suggested that vitamin C and E might reduce pre-eclampsia in all pregnant women, not just those with type 1 diabetes. Since then however, subsequent larger trials found no benefit of vitamin C and E supplementation during regular pregnancies.
Several previous research studies had also previously suggested that because type 1 diabetes is associated with both increased oxidative stress (and a reduction in antioxidants), antioxidant vitamin supplements could improve outcomes for these women.
To investigate further, the Diabetes and Pre-Eclampsia Intervention Trial (DAPIT) study group examined the benefits of 1000mg vitamin C and 400 IU (international units) vitamin E in 762 pregnant women with type 1 diabetes, recruited from 25 UK antenatal clinics in the UK. Women were randomly assigned to vitamins (379) or placebo (383) daily from between 8 and 22 weeks until delivery.
Overall, findings showed that the rate of pre-eclampsia was similar in both groups (15 per cent vs 19 per cent). In women with low antioxidant status at the start of the study however, taking vitamins was associated with a significantly lower risk of pre-eclampsia.
There was no evidence of harm from vitamin supplementation to either mothers or babies. Antioxidant vitamins did not increase the likelihood of developing high blood pressure during pregnancy (11 per cent vs 11 per cent) and actually tended to reduce the risk of having a low birthweight baby (6 per cent vs 10 per cent). Additionally, fewer babies were born preterm to women taking vitamin C.
Professor Ian Young from the Centre for Public Health, Queen’s School of Medicine, Dentistry and Biomedical Sciences said: “Dietary intervention rich in various antioxidants might have benefits that cannot be replicated by individual supplements. Alternatively, prescription of antioxidant vitamins at 8–22 weeks’ gestation might be too late to affect the pathological process for most patients with diabetes.”“
In principle, the notion that oxidative stress is implicated in the cause and development of pre-eclampsia remains plausible, but the benefit of vitamin supplementation might be limited to women with vitamin depletion; however, this idea needs confirmation.
”Baha M Sibai from the University of Cincinnati, Ohio, USA, said: “The causes of pre-eclampsia might be multi-factorial. Some cases might be caused by immunological factors, others by dietary factors, and others because of pre-existing medical conditions, or by a combination of these factors. Therefore any single intervention is unlikely to be effective in prevention.” The research is being presented at the American Diabetes Association meeting in Florida this weekend.
The article will be published online first in The Lancet. Media inquiries to Lisa McElroy, Press and PR Unit, 0781 44 22 572 or email firstname.lastname@example.org