Gowachirapant 2014.

Methods	Study design: randomised double‐blind controlled trial with 2 arms Unit of allocation: individual Time period of recruitment and data collection: Thailand: October 2008‐June 2013
Participants	Description: pregnant women in the first trimester Location/setting: Ramathibodi Hospital of Mahidol University in Bangkok, Thailand How participants were recruited and selected: recruited among those who registered at the Ramathibodi Hospital Inclusion criteria: singleton pregnancy, 18‐40 years of age, gestational age ≤ 14 weeks, non‐lactating, generally healthy (no history of thyroid disorders), and not taking any iodine supplement Exclusion criteria: TSH > 6.0 mIU/L at screening Sample size: 511 women enrolled and randomised in Thailand Age: not reported Socioeconomic status: not reported Nutritional status: 4% obese and 10%‐13% overweight Baseline iodine status of participants/area: described by authors as mild deficiency (UIC 110‐112 µg/L) Baseline coverage of iodized salt: 88%‐89% purchased iodized salt for the household Breastfeeding practices: not reported Other important information about participants or setting: at baseline, 40% (placebo group) and 47% (iodine group) were uniparous, 4.7% has subclinical hyperthyroidism and 8.6% had subclinical hypothyroidism
Interventions	Experimental intervention: oral iodine supplementation Total number randomised: n = 262 Timing: starting in the first trimester Form: oral iodine tablets Frequency and duration: daily until delivery Iodine compound: potassium iodide Iodine dose: 200 µg elemental iodine Other nutrients: see co‐interventions below Adherence: not reported (assessed by counting the tablets returned after delivery; good compliance was defined as taking 80% of prescribed treatment) Control/comparison intervention: placebo Total number randomised: n = 249 Description: identical tablet Adherence: not reported Co‐intervention(s): multiple vitamin‐mineral tablets without iodine, also until delivery
Outcomes	Pregnancy: thyroid function (TSH, free and total T4 and T3, Tg, thyroid antibodies), UIC and thyroid gland volume in the 2nd and 3rd trimester Postpartum: thyroid function, UIC and thyroid gland volume 6 weeks postpartum Infant/child: birth characteristics (from hospital records) and thyroid gland volume at delivery and 6 weeks of age, thyroid function (TSH only?) at delivery from cord blood, spot UIC at 6 weeks of age, Neonatal behavioural assessment scales at 6 weeks of age (Table 8)
Notes	Trial was also conducted in India but we have not yet located any reports with those data
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	“women were allocated to two treatment groups by simple randomisation.”
Allocation concealment (selection bias)	Unclear risk	Allocation concealment method was not clear
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Subjects, caregivers and investigators were blinded
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Outcome assessors were blinded
Incomplete outcome data (attrition bias) All outcomes	High risk	Loss to follow‐up was 19%‐20% at the first follow‐up visit (second trimester) and > 20% for all subsequent visits, with 58%‐59% having 6 weeks' postpartum data (though loss was balanced between the groups and for similar reasons)
Selective reporting (reporting bias)	Unclear risk	Unclear. More data were collected (through 24 months of age and in India) but to date only this PhD thesis has been published
Other bias	Unclear risk	Appears to be free of other sources of bias