Dalton 1962.

Methods	Randomisation: women allocated 'at random' to 2 groups. No further information. Allocation concealment: 'numbered envelope system'. No further information. Follow up: 22/150 (15%) excluded from analysis: 14 from progesterone arm (3 raised BP at booking, 2 withdrew booking, 1 abortion, 8 opted out), and 8 from control arm (3 raised BP at booking, 3 withdrew booking, 1 abortion, 1 opted out). Blinding: participant and caregiver not blinded, and blinding of outcome assessment not reported.
Participants	128 women between 16‐28 weeks' gestation with 2 or more 'toxaemic symptoms' (nausea, vomiting, lethargy, backache, headache, vertigo, fainting, cramp, or paraesthesia), blood pressure < 140/90 mmHg and no albuminuria.
Interventions	Progesterone: 100 mg IM daily or on alternate days for 1 week. On subsequent visits, dose and frequency of injection adjusted depending on symptoms (range 300 mg daily to 50 mg on alternate days). Progesterone stopped if symptoms disappeared (in one‐third of the participants, before 34 weeks) or when labour started. Control: simple medication to relieve symptoms based on individual needs: such as alkalis, analgesics, sedatives, antihistamines. Administered as mixtures, tablets, capsules, or powders.
Outcomes	Woman: PE (BP > 140/90 mmHg + either oedema or albuminuria after 28 weeks); side effects in progesterone group only. Baby: stillbirth or neonatal death.
Notes	385 women interviewed, 150 eligible and agreed to recruitment. Definition of PE included oedema, so these data likely to be overestimated (2 in progesterone arm vs 7 in control arm). Numbers with proteinuria (1 vs 5) likely to be better estimate of PE, and used for review. Child development at age 1 year; intelligence and personality at 16 years of age reported. Data excluded due to large losses to follow up (54% at 1 year and 80% at 16 years).
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Inadequate information for assessment.
Allocation concealment (selection bias)	Unclear risk	Inadequate information for assessment.
Blinding (performance bias and detection bias) All outcomes	High risk	Participants and personnel not blinded.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Attrition 15% but appears to be balanced across groups.
Selective reporting (reporting bias)	High risk	No data on serious maternal morbidity. Side effects reported for progesterone group only.
Other bias	High risk	Although long‐term follow up attempted, large losses to follow‐up.