Netherlands 1998.

Methods	Randomisation: random numbers in blocks of 10. Stratified by centre. Allocation concealment: sealed, numbered, opaque envelopes. Follow up: no loss to follow up (A). Blinding: participants not blinded. Caregiver blinded only to urinary sodium concentration. Blinding of outcome assessment not reported.
Participants	361 women booked for midwifery care, nulliparous, DBP < 90 mmHg at booking visit before 20 weeks. Randomised if DBP > 85 x 2 in subsequent visit, or weight gain > 1 kg/week for 3 consecutive weeks, or excess oedema. Excluded if planning to leave the city or risk factors for PIH.
Interventions	Low: sodium‐restricted diet, aimed at less than 50 mmol/day. Written dietary instructions given by midwife. Normal: asked not to change eating habits.
Outcomes	Woman: highest DBP, PE (HT (not defined) with significant proteinuria (not defined)), eclampsia, hospital referrals and admissions for HT, time to delivery, abruption, mode of delivery. Baby: death, gestation at delivery (mean), birthweight, Apgar at 5 minutes, NICU admission.
Notes	Multicentre study: 9 centres. Setting: midwifery practices and hospital clinic. Mean urinary sodium after randomisation 84 mmol/day in low sodium group, 124 mmol/day for normal diet.
Risk of bias
Bias	Authors' judgement	Support for judgement
Allocation concealment?	Low risk	A ‐ Adequate

DBP: diastolic blood pressure 
 GH: gestational hypertension 
 HT: hypertension 
 hr: hour 
 NICU: neonatal intensive care unit 
 PE: pre‐eclampsia 
 PIH: pregnancy induced hypertension 
 SGA: small‐for‐gestational age