Rostami 2017.

Methods	Eight‐arm blind randomised clinical trial
Participants	Women with a GA < 14 weeks based on lLMP or obstetrical estimation, with a singleton pregnancy, and who had planned to receive ongoing prenatal and delivery in the Masjed‐Soleyman. Participants were excluded if they consumed multivitamins containing more than 400 international units (IU) per day of vitamin D3; used anticonvulsants; and had history of chronic diseases like diabetes, hypertension, renal dysfunction, liver diseases, and complicated medical or obstetrical history
Interventions	Women randomised by levels of vitamin D in serum Participants with moderate deficiency I1: 50,000 IU of oral D3 weekly for a total duration of 6 weeks I2: 50,000 IU of oral D3 weekly for a total duration of 6 weeks and then a monthly maintenance dose of 50,000 IU of D3 until delivery I3: a single dose of intramuscular administration of 300,000 IU of D3 I4: a single dose of intramuscular administration of 300,000 IU of D3 and then a monthly maintenance dose of 50,000 IU of D3 until delivery Participants with severe deficiency I5: 50,000 IU of oral D3 weekly for a total duration of 12 weeks I6: 50,000 IU of oral D3 weekly for a total duration of 12 weeks and then a monthly maintenance dose of 50,000 IU of D3 until delivery I7: intramuscular administration of 300,000 IU of D3; 2 doses for 6 weeks I8: intramuscular administration of 300,000 IU of D3; 2 doses for 6 weeks, followed by a monthly maintenance dose of 50,000 IU of D3 until delivery Health worker cadre: the study was conducted at prenatal care centres of urban areas of Masjed‐Soleyman and Shushtar, Iran; 2 cities with similar cultural, geographic, nutritional habits, and sun exposure conditions; 1 of these cities (Masjed‐Soleyman) was assigned to intervention. Masjed‐Soleyman County is in the northeast of Khuzestan province. Its area is 9/6327 km2 with a population of 103,369 people with Persian ethnicity. This is a sunny region with a hot and humid climate. Its altitude is 260 metres above sea level. In terms of geographical location, it is between 31°59′ E longitude and 49°17′ N latitude. Shushtar County is in the north of Khuzestan. Its area is 2436 km2 with a population of 192,361 people with Persian ethnicity. The climate is similar to Masjed‐Soleyman. Its altitude is 150 metres above sea level. In terms of geographical location, it is between 48°20′ E longitude and 32°30′ N latitude. Outside of Tropics Midwives responsible for prenatal care in the selected health centres. The dedicated study midwife treating the females, who did not participate in any subsequent phases of the study, was the only person who knew the group each patient belonged to (single‐blinded). Biostatistician Research assistant who assigned sealed opaque envelopes to each participant Health care workers, who received complaints about adverse side effects. Health workers (blinded to treatment allocation) who determined pregnancy outcomes Physicians, who participated in various phases of the study, and were blinded to grouping of women Technician, who analysed laboratory samples.
Outcomes	Maternal Primary Pre‐eclampsia Gestational diabetes Secondary Serum concentration of 25(OH)D at delivery Type of delivery (caesarean section versus vaginal) Infant Primary Preterm delivery Secondary (infant) Head circumference Height Birthweight Apgar score Serum cord concentration of 25(OH)D Laboratory method used for assessment of vitamin D concentrations: circulating 25(OH) levels were measured using enzyme‐linked immunosorbent assay (ELISA) method and a kit of Immunodiagnostics Systems Ltd (IDS Ltd) by Auto Analyzer (Human Corporation, Germany). This 25(OH)D assay is FDA‐cleared for clinical use in the USA. The inter‐ and intra‐assay coefficient of variations were 3.891% and 3.37%, respectively (sensitivity of 5nmol/L). Calibration of the instruments was done as per the manufacturer's instructions and validation studies were done prior to the test. Samples were analysed by a single technician using the same equipment throughout the study in a reference laboratory and were measured according to the standard operating procedures.
Notes	• Start of supplementation: July 1‐September 31, 2014 • Pre‐gestational BMI (kg/m2): unknown/mixed • Supplementation scheme/regimen: sIngle, weekly, monthly • Skin pigmentation based on Fitzpatrick skin tone chart (Fitzpatrick 1988): not available • Latitude: outside of Tropics • Season at the start of pregnancy: summer/autumn Source of funding: this work was financially supported by the Research Institute of Endocrine Sciences (grant number; 493). Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences http://dx.doi.org/10.13039/501100007427, 493, Fahimeh Ramezani Tehrani. Dates of the study: July 1‐September 31, 2014. Declarations of interest among primary researchers: none reported. The authors provided additional data by email which were incorporated into the meta‐analysis.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Participants in each group of severe or moderate deficiencies were randomly divided into 4 subgroups using a computer‐generated list/permuted block randomisation by a biostatistician to achieve balance across treatment groups. The number of participants per block was 8.
Allocation concealment (selection bias)	Low risk	Sealed opaque envelopes were assigned to each participant by a research assistant not associated in the trial.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Physicians, who participated in various phases of the study, were blinded to grouping of women; only the midwife, who did not participate in any phase of the study, was aware of the group that each patient was in.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Physicians, who participated in various phases of the study, were blinded to grouping of women; only the midwife, who did not participate in any phase of the study, was aware of the group that each patient was in.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Lost to follow‐up was low. Moderate deficiency group: n = 400; I1: n = 100, 2 miscarriages, I2: n = 100, 1 miscarriage, I3 n = 100, 1 miscarriage, 2 discontinued participation), I4:n = 100. Severe deficiency group: I5: n = 100, 1 miscarriage, 1 discontinued participation, I6:n = 100, 2 miscarriages, I7:n = 100, 1 miscarriage, I8:n = 100, 1 miscarriage.
Selective reporting (reporting bias)	High risk	Outcomes not reported as pre‐specified or expected.
Other bias	Unclear risk	Insufficient information to allow judgement.