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Taking folate in pregnancy and risk of maternal breast cancer

BMJ 2004; 329 doi: (Published 09 December 2004) Cite this as: BMJ 2004;329:1375
  1. Deborah Charles, research assistant1,
  2. Andy R Ness (, senior lecturer in epidemiology2⇑,
  3. Doris Campbell, reader in obstetrics and gynaecology1,
  4. George Davey Smith, professor of clinical epidemiology3,
  5. Marion H Hall, emeritus professor1
  1. 1 Dugald Baird Centre For Research on Women's Health, Department of Obstetrics and Gynaecology, Aberdeen Maternity Hospital, Aberdeen AB25 2ZL
  2. 2 Unit of Paediatric and Perinatal Epidemiology, Division of Child Health, Bristol BS8 1TQ
  3. 3 Department of Social Medicine, University of Bristol, Bristol B58 2PR
  1. Correspondence to: A R Ness
  • Accepted 7 October 2004


Taking folate before conception and then for the first three months of pregnancy reduces the risk of recurrence of neural tube defects,1 and fortification of food has been proposed. The effects of long term exposure to high concentrations of supplemental folate are unknown, and antimetabolite effects are theoretically possible.2 Data on the long term effects of increased folate intake in pregnancy are limited. We followed up a large trial of folate supplementation in pregnancy from the 1960s.3 4 We examined the association between folate status and death, and we also analysed the effects of folate supplementation.

Participants, methods, and results

From June 1966 to June 1967, 3187 women were identified as potentially eligible for a trial of folate supplementation.3 4 At her booking visit, the mother's age, gestation, parity, weight, and blood pressure were recorded, and blood was taken to …

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