Taking vitamins C and E during pregnancy does not lower the risk of pre-eclampsia in women with type 1 diabetes. However, vitamin supplementation could be beneficial in women with a low antioxidant status and needs further investigation, according to an Article published Online First in The Lancet and being presented at the American Diabetes Association meeting in Florida, USA. Interestingly, contrary to previous research, the report shows no evidence of vitamin C and E supplements causing any harm to mothers or babies.
The causes of pre-eclampsia are not known, but it has been suggested that oxidative stress* 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 pregnant women. However, several subsequent larger trials found no benefit of vitamin C and E supplementation during pregnancy.
Women with type 1 diabetes are at high risk of pre-eclampsia and preterm delivery. It has been suggested that because type 1 diabetes is associated with increased oxidative stress and a reduction in antioxidants, antioxidant vitamins might improve outcomes in this specific group of patients.
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' gestation until delivery.
Overall, findings showed that the rate of pre-eclampsia was similar in both groups (15% vs 19%). However, in women with low antioxidant status at the start of the study, 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% vs 11%) and appeared to reduce the risk of having a low birthweight baby (6% vs 10%). Additionally, fewer babies were born preterm to women taking vitamin C.
These findings, say the authors, suggest that: "Dietary intervention rich in various antioxidants might have benefits that cannot be replicated by individual supplements. Alternatively, prescription of antioxidant vitamins at 8 weeks' gestation might be too late to affect the pathological process for most patients with diabetes."
They conclude: "In principle, the notion that oxidative stress is implicated in pathogenesis of pre-eclampsia remains plausible, but the benefit of vitamin supplementation might be limited to women with vitamin depletion; however, this idea needs confirmation."
In a Comment, Baha M Sibai from the University of Cincinnati, Ohio, USA, cautions that: "The placebo group in DAPIT contained more women with previous pre-eclampsia, chronic hypertension, and nephropathy (factors that increase the rates of the above complications) than did the supplementation group…because the DAPIT investigators did not adjust for all the above factors in women with low antioxidant status, the conclusions for this group might not be valid."
He concludes: "The aetiology 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."
Professor David R McCance, Royal Victoria Hospital, Belfast, UK.T) +44 (0)795 803 6242 david.mccance@belfasttrust.hscni.net
Professor Ian Young, Queen's University Belfast, Belfast, UK. T) +44 (0)772 521 7425 (mobile) E) i.young@qub.ac.uk
Dr Valerie Holmes, University Belfast, Belfast, UK. T) +44 (0)778 866 2550 (mobile) E) v.holmes@qub.ac.uk
Dr Baha M Sibai, University of Cincinnati, Ohio, USA. T) +1 513 558 8449 E) baha.sibai@uc.edu
For full Article and Comment, see: http://press.thelancet.com/adavitcvite.pdf
Notes to Editors: *Oxidative damage has been implicated in many diseases such as diabetes and cancer. To counteract oxidative stress, the body produces antioxidants to neutralise free radicals that can harm cells. It has been suggested that increasing the intake of antioxidant supplements could help prevent such diseases.
Journal
The Lancet