Netherlands 1998.

Methods	Sealed numbered opaque envelopes. Blocks of 10 stratified by centre.
Participants	361 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.
Interventions	Low: sodium restricted diet, aimed at less than 50mmol/day. Written dietary instructions given by midwife. Normal: asked not to change eating habits.
Outcomes	Woman: 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.
Notes	Multicentre study involving 8 midwifery practices. Mean urinary sodium after randomisation 84mmol/day in low sodium group, 124mmol/day for normal diet.
Risk of bias
Bias	Authors' judgement	Support for judgement
Allocation concealment?	Low risk	A ‐ Adequate

DBP=diastolic blood pressure, PIH=pregnancy induced hypertension, PE=pre‐eclampsia, HT=hypertension