Pyridoxine (vitamin B6) supplementation in pregnancy
Mahomed K, Gulmezoglu AM
Date of most recent substantive amendment: 21 October 1996
This review should be cited as: Mahomed K, Gulmezoglu AM.
Pyridoxine (vitamin B6) supplementation in pregnancy (Cochrane
Review). In: The Cochrane Library, Issue 2, 2003. Oxford: Update
Software.
CD000179
ABSTRACT
Background
Pyridoxine (vitamin B6) contributes to the development of the central nervous system and may influence brain development and cognitive function. It may also prevent dental caries and protect the placental vascular bed.
Objectives
The objective of this review was to assess the effects of vitamin B6 supplementation during pregnancy and labour.
Search Strategy

We searched the Cochrane Pregnancy and Childbirth Group trials register.
Selection Criteria
Randomised trials of pyridoxine administration compared to a control group.
Data collection and analysis
Trial quality was assessed and data were extracted by two reviewers.
Main Results
One trial involving 371 women was included. Pyridoxine supplementation either as oral capsules (odds ratio 0.63, 95% confidence interval 0.41 to 0.95) or lozenges (odds ratio 0.33, 95% confidence interval 0.22-0.51) was associated with decreased incidence of dental decay in pregnant women.
Reviewers' conclusions
There is not enough evidence to evaluate pyridoxine supplementation during pregnancy, although the results of one trial suggest that it may have a beneficial effect on dental decay.
This review should be cited as:
Mahomed K, Gulmezoglu AM Pyridoxine (vitamin B6) supplementation in pregnancy (Cochrane Review). In: The Cochrane
Library, Issue 2, 2003. Oxford: Update Software.

BACKGROUND
Pyridoxine (vitamin B6) contributes to the development of central nervous system and may influence brain development and cognitive function. Although vitamin B6 indices seem to decrease during pregnancy, it is not clear whether normal pregnancy is associated with a vitamin B6 deficient state or not, and even if this is the case, whether this has any clinical significance is not known. Pyridoxine therapy has been researched most extensively for the prevention of nausea and vomiting during pregnancy (see separate review by
Jewell et al 1996). However, interest in pyridoxine has also included possible prevention of dental caries and protection of the placental vascular bed.
This review will evaluate trials in which pyridoxine was administered during pregnancy and/or labour for purposes other than treatment of nausea and vomiting.
OBJECTIVES

To evaluate the effects of Vitamin B6 supplementation throughout pregnancy and in labour.
CRITERIA FOR CONSIDERING STUDIES FOR THIS REVIEW
Types of studies
All acceptably controlled studies of pyridoxine administration in pregnancy and labour.
Types of participants
Pregnant women, either during the prenatal period or labour.
Types of intervention
Pyridoxine (vitamin B6) administration compared with a nonpyridoxine group (control).
Types of outcome measures
Antenatal supplementation: Dental decay
Intrapartum supplementation: Neonatal outcome.
SEARCH STRATEGY FOR IDENTIFICATION OF STUDIES
See: Cochrane Pregnancy and Childbirth Group search strategy

This review has drawn on the search strategy developed for the
Pregnancy and Childbirth Group as a whole.
Relevant trials were identified in the Group's Specialised Register of
Controlled Trials. See Review Group's details for more information.
METHODS OF THE REVIEW
Trials under consideration were evaluated for methodological quality and appropriateness for inclusion without consideration of their results.
Included trial data were processed as described in Chalmers 1989
DESCRIPTION OF STUDIES
See table of 'Characteristics of included studies'.
METHODOLOGICAL QUALITY

Although the method of randomly assigning women to three groups is not stated, the single trial included seems to have been executed carefully to minimise bias. Placebos were used and outcome assessments were made by dentists not involved in the trial.
RESULTS
Hillman et al (Hillman 1962) studied the effects of two types of pyridoxine supplementation on dental decay. Both local and systemic pyridoxine supplementation were associated with improvements in dental decay assessments with the local application showing a stronger effect when compared to placebo.
DISCUSSION
See 'Conclusions'.
REVIEWER'S CONCLUSIONS

Implications for practice
The available evidence provides no basis for recommending pyridoxine supplementation during pregnancy.
Implications for research
Better evidence about the effects of pyridoxine supplementation is required. Whether this is regarded as a research priority may depend on whether dental decay is a significant problem in the community concerned; the information which seems most likely to be valid suggests that local application of Vitamin B6 may be protective.
ACKNOWLEDGEMENTS
None.
POTENTIAL CONFLICT OF INTEREST
None known.

TABLES
Characteristics of included studies
Study Hillman 1962
Methods Women were randomly assigned to three groups. Placebos were used, clinical and radiological assessments were blinded.
Participants Urban, antenatal clinic attenders, less than four months pregnant.
Interventions Women were divided into three groups:
1. Multivitamin capsule + placebo lozenges
2. Multivitamin capsule containing 20 mg pyridoxine + placebo lozenges
3. Multivitamin capsule + pyridoxine lozenges (20 mg/d).
Outcomes Number of decayed-missing-filled teeth.
Notes
Allocation concealment A
Characteristics of excluded studies

Study Reason for exclusion
Lumeng 1976 Reasons for excluding this study were: (1) there was no non-vitamin B6 control group (2) biochemical outcomes only were studied. Thirty-three antenatal women were randomly assigned to multivitamin supplements containing 2.5, 4 or 10 mg pyridoxine.
Swartwout 1960 Antenatal women were given 25 mg pyridoxine or placebo in a double-blind way in this randomized controlled trial. The main outcome of interest was histological changes in the placental arterioles. The supplemented group had higher birth and placental weights but no other clinical information was given.
Temesvari 1983 Main reason for exclusion was that no clinical outcomes were reported in this study. Women presenting at the delivery room were randomly assigned to 1) Pyridoxine HCl 100 mg intramuscularly, 2) Pyridoxine HCl 100 mg oral and 3) No pyridoxine.
After delivery cord blood samples were taken for P50 and prolactin measurements.
REFERENCES
References to studies included in this review
Hillman 1962 {published data only}

Hillman RW, Cabaud PG, Schenone RA. The effects of pyridoxine supplements on the dental caries experience of pregnant women. Am
J Clin Nutr 1962;10:512-5.
References to studies excluded from this review
Lumeng 1976
Lumeng L, Cleary RE, Wagner R, Yu P-L, Li T-K. Adequacy of
Vitamin B6 supplementation during pregnancy: a prospective study.
Am J Clin Nutr 1976;29:1376-83.
Swartwout 1960
Swartwout JR, Unglaub WG, Smith RC. Vitamin B6, serum lipids and placental arteriolar lesions in human pregnancy. A preliminary report.
Am J Clin Nutr 1960;8:434-44.
Temesvari 1983
Temesvari P, Szilagyi I, Eck E, Boda D. Effects of an antenatal load of pyridoxine (Vitamin B6) on the blood oxygen affinity and prolactin levels in newborn infants and their mothers. Acta Paediatr Scand
1983;72:525-9.

Additional references
Chalmers 1989
Chalmers I, Hetherington J, Elbourne D, Keirse MJNC, Enkin M. In:
Chalmers I, Enkin MW, Keirse MJNC, editor(s). Effective Care in
Pregnancy and Childbirth. Vol. 1, Oxford: Oxford University Press,
1989.
Jewell et al 1996
Jewell D, Young G. Treatments for nausea and vomiting in early pregnancy (Cochrane Review). In: The Cochrane Library, 1, 1997.
Oxford: Update Software.
COMMENTS AND CRITICISMS
Hughes, December 2002
Summary:
Please mention the possibility of side effects with pyridoxine, in particular peripheral neuropathy, and suggest what would be a safe dose if it were used.

Author's Reply:
A response from the reviewer will be published as soon as it is available.
Contributors:
Summary of comment received from Richard Hughes, December
2002.
GRAPHS
To view a graph or table, click on the outcome title of the summary table below.
To view graphs using MetaView: select "Outline" on the menu bar, then scroll down to Links and then click on Metaview graphs.
01 Pyridoxine vs no supplementation
Outcome title No. of studies No. of participants Statistical method
Effect size

01 Increased dental decay (capsules vs placebo) 1 371 Peto OR
[95% CI] 0.63 [0.41, 0.95]
02 Increased dental decay (lozenges vs placebo) 1 342 Peto OR
[95% CI] 0.33 [0.22, 0.51]
COVER SHEET
Title Pyridoxine (vitamin B6) supplementation in pregnancy
Reviewer(s) Mahomed K, Gulmezoglu AM
Contribution of reviewer(s) Information not supplied by reviewer
Issue protocol first published Information not available
Issue review first published 1997/2
Date of most recent amendment Information not available
Date of most recent SUBSTANTIVE amendment 21 October 1996
Most recent changes Information not supplied by reviewer
Date new studies sought but none found Information not supplied by reviewer
Date new studies found but not yet included/excluded Information not supplied by reviewer

Date new studies found and included/excluded Information not supplied by reviewer
Date reviewers' conclusions section amended Information not supplied by reviewer
Contact address Prof Kassam Mahomed
Obstetrician Gynaecologist
Port Pirie Regional Health Service
PO Box 546
Port Pirie
5540
South Australia
AUSTRALIA
( +61 8 86384500 mahomed.kassam@saugov.sa.gov.au fax: +61 8 86384568
Cochrane Library number CD000179
Editorial group Cochrane Pregnancy and Childbirth Group
Editorial group code HM-PREG
SOURCES OF SUPPORT

External sources of support
Nuffield Provincial Hospitals Trust, UK UK
Internal sources of support
No sources of support supplied
Index Terms
Medical Subject Headings (MeSH)
Dietary Supplements ; Pyridoxine
Mesh check words: Female Human Pregnancy
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GRAPHS