Intervention Review

You have free access to this content

Reduced salt intake compared to normal dietary salt, or high intake, in pregnancy

  1. Lelia Duley1,*,
  2. David J Henderson-Smart2

Editorial Group: Cochrane Pregnancy and Childbirth Group

Published Online: 26 JUL 1999

Assessed as up-to-date: 10 MAY 1999

DOI: 10.1002/14651858.CD001687

How to Cite

Duley L, Henderson-Smart DJ. Reduced salt intake compared to normal dietary salt, or high intake, in pregnancy. Cochrane Database of Systematic Reviews 1999, Issue 3. Art. No.: CD001687. DOI: 10.1002/14651858.CD001687.

Author Information

  1. 1

    University of Leeds, Centre for Epidemiology and Biostatistics, Bradford, West Yorkshire, UK

  2. 2

    Queen Elizabeth II Research Institute, NSW Centre for Perinatal Health Services Research, Sydney, NSW, Australia

*Lelia Duley, Centre for Epidemiology and Biostatistics, University of Leeds, Bradford Royal Infirmary, Bradford Institute of Health Research, Temple Bank House, Duckworth Lane, Bradford, West Yorkshire, BD9 6RJ, UK.

Publication History

  1. Publication Status: Edited (no change to conclusions)
  2. Published Online: 26 JUL 1999


Characteristics of included studies [ordered by study ID]
Netherlands 1997

Methods"Closed envelope system", no further information. 28 women (10%) women excluded. Low salt 23 excluded: 17 refused diet, 3 social reasons, 2 medical reasons, 1 fetal trisomy. Normal salt 5 excluded: 2 social reasons, 3 medical reasons.

Participants270 nulliparous women with a singleton pregnancy after 12 weeks, by dates and ultrasound. Excluded if pre-existing HT, diabetes, renal disease, cardiovascular disease.

InterventionsLow: diet with about 20mmol sodium per day. Oral and written instruction by dietician, no added salt and ready made foods only if no salt in preparation.
Normal: no dietary restriction.

OutcomesWoman: PIH, PE, severe HT, small for gestational age, preterm delivery
Baby: death.

NotesMean urinary sodium after randomisation was around 70mmol/day in the low sodium group and 135mmol/day in the normal diet group.

Risk of bias

ItemAuthors' judgementDescription

Allocation concealment?UnclearB - Unclear

Netherlands 1998

MethodsSealed numbered opaque envelopes. Blocks of 10 stratified by centre.

Participants361 women booked for midwifery care, nulliparous, DBP <90mmHg at booking visit before 20 weeks. Randomised if DBP >85 x2 in subsequent visit, or weight gain >1kg/week for 3 consecutive weeks, or excess oedema. Excluded if planning to leave the city or risk factors for PIH.

InterventionsLow: sodium restricted diet, aimed at less than 50mmol/day. Written dietary instructions given by midwife.
Normal: asked not to change eating habits.

OutcomesWoman: highest DBP, pre-eclampsia, eclampsia, referrals and admissions for hypertension, time to delivery, abruption, mode of delivery.
Baby: gestation at delivery (mean), birthweight, Apgar at 5 minutes, paediatric admission, death.

NotesMulticentre study involving 8 midwifery practices. Mean urinary sodium after randomisation 84mmol/day in low sodium group, 124mmol/day for normal diet.

Risk of bias

ItemAuthors' judgementDescription

Allocation concealment?YesA - Adequate

Characteristics of excluded studies [ordered by study ID]

StudyReason for exclusion

Australia 1986aNo clinical outcomes reported.

Participants: 58 primigravid women.
Intervention: one week of either high salt or low salt diet.
Study design: 'assigned randomly'.

Australia 1986bNo clinical outcomes reported.

Participants: 40 primigravid women.
Intervention: one week of either high salt or low salt diet.
Study design: 'assigned randomly'.

UK 1958Not a randomised trial. Quasi random, using alternate allocation of women attending clinic.

Participants: 2077 women at booking clinic, 58 excluded.
Intervention: high salt diet with advice to add salt to diet and eat salty food versus low salt with advice to avoid adding salt to food and not to eat salty food.

UK 1961Not a randomised trial. Allocation by ward and by consultant.

Participants: 739 women with high blood pressure, oedema and proteinuria. Excluded if <24 hours from admission to delivery.
Interventions: 2g salt versus 10g versus 25g.

USA 1961Not a randomised trial. Quasi random using alternate allocation.

Participants: 48 women with pre-eclampsia.
Interventions: 1-2g salt versus 10-12g.

Comparison 1. Low vs normal salt intake in pregnancy

Outcome or subgroup titleNo. of studiesNo. of participantsStatistical methodEffect size

 1 Hypertension1242Risk Ratio (M-H, Fixed, 95% CI)0.98 [0.49, 1.94]

 2 Pre-eclampsia2603Risk Ratio (M-H, Fixed, 95% CI)1.11 [0.46, 2.66]

 3 Referral to hospital, no admission1361Risk Ratio (M-H, Fixed, 95% CI)1.05 [0.48, 2.32]

 4 Admission to hospital1361Risk Ratio (M-H, Fixed, 95% CI)0.82 [0.56, 1.22]

 5 Placental abruption1361Risk Ratio (M-H, Fixed, 95% CI)0.19 [0.01, 3.98]

 6 Caesarean section1361Risk Ratio (M-H, Fixed, 95% CI)0.75 [0.44, 1.27]

 7 Perinatal mortality2409Risk Ratio (M-H, Fixed, 95% CI)1.92 [0.18, 21.03]

 8 Birthweight <10th centile1242Risk Ratio (M-H, Fixed, 95% CI)1.5 [0.73, 3.07]

 9 Birthweight <2500g1361Risk Ratio (M-H, Fixed, 95% CI)0.84 [0.42, 1.67]

 10 Preterm delivery1242Risk Ratio (M-H, Fixed, 95% CI)1.08 [0.46, 2.56]

 11 Apgar at 5 min <71361Risk Ratio (M-H, Fixed, 95% CI)1.37 [0.53, 3.53]

 12 Paediatric admission1361Risk Ratio (M-H, Fixed, 95% CI)0.98 [0.69, 1.40]