Olsen 1992.

Methods	NCT01353807 3‐arm RCT in a ratio of 2:1:1: for fish oil, olive oil, and no supplement
Participants	533 women randomised Inclusion criteria: healthy women, at approximately 30 weeks' gestation, aged 18‐44 years Exclusion criteria: history of placental abruption, a serious bleed in the current pregnancy, use of PG inhibitors, multiple pregnancy, fish allergy or regular intake of fish oil Setting: main midwifery clinic, Aarhus, Denmark
Interventions	SUPPLEMENTATION: omega‐3 versus olive oil versus no supplement Group 1: fish oil (2.7 g omega‐3 fatty acids/day) given as 4 x 1 g capsules/day containing fish oil (Pikasol 32% EPA (20:5n‐3), 23% DHA (22:6n‐3)) and 2 mg tocopherol/mL: total number randomised = 266 Group 2: 4 x 1 g capsules olive oil/day: total number randomised = 136 Group 3: no supplement: total number randomised = 131 Timing of supplementation: from ˜30 weeks GA to birth DHA + EPA dose/day: high: 864 mg DHA + 621 mg EPA
Outcomes	Women/birth: SBP and DBP, PIH, PE, food frequency questionnaire*, preterm birth < 37 weeks, caesarean, congenital anomalies, blood loss, maternal adverse effects Babies/infants/children/adults: stillbirth, duration of gestation, birthweight, birth length, BMI At 16‐year follow‐up: asthma, atopic dermatitis, allergic rhinitis At 19‐year follow‐up: insulin, glucose, glycated Hb, leptin, adiponectin, insulin‐like growth factor 1, high sensitivity CRP, height, weight, BMI, waist circumference *enabled women to be classified into low, medium and high habitual intake of fish
Notes	Sample size estimates were done but not reported in the papers because they were regarded as posthoc by authors (personal communication). Women completed baseline information regarding fish intake. Outcome assessment was blinded, but 85% of women in the fish oil group correctly identified their group allocation, whereas for olive oil 50% identified the correct oil. Funding: "This study was supported by the Danish Medical Research council (J No 12‐9052) and 12‐9144), Sygekassernes Helsefond, Weirnan's Legat and Michaelsen Fonden". Capsules were provided by Lube Ltd, Hadsund, Denmark. Follow‐up was supported by the EU FP5 consortium, Early Nutrition Programming Project, NIH, The Danish Strategic Research Council, The Danish Heart Foundation, The Novo Nordisk Foundation, The Danish Diabetes Foundation, The Aase and Ejnar Danielsens Foundation, and the National Center for Complementary and Alternative Medicine. Declarations of interest: JE Chavarro and Sjurdur F Olsen received research support from the NIH. The rest of the authors declared that they had no relevant conflicts of interest.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Stratified and block randomisation
Allocation concealment (selection bias)	Low risk	A sealed, opaque envelope containing a randomisation number which identified either a particular package of oil capsules or no treatment.
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Capsules and their boxes looked identical for fish oil and olive oil; however the no treatment group was unblinded.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not reported, apart from that at 19‐year follow‐up outcome assessors were blinded to group allocation.
Incomplete outcome data (attrition bias) All outcomes	Low risk	No post‐randomisation exclusions and no losses to follow‐up; at 19‐year follow‐up: n = 243 completed physical examination (out of 517 mother/child dyads alive and still living in Denmark); 41% were from the fish oil group and 53% were from the olive oil/no oil group.
Selective reporting (reporting bias)	Low risk	Most expected outcomes were reported.
Other bias	Low risk	Similar baseline characteristics