Mutlu 2014.

Methods	Randomised clinical trial
Participants	At least 16 years old and up to 42 years old (traditional dressing style), with a singleton pregnancy, having no previously known Cancer or untreated thyroidal disorders
Interventions	Women randomised to: ‐ Group 1: 1200 IU/d of vitamin D3; ‐ Group 2: 2000 IU/d form of vitamin D3 (50,000 units of cholecalciferol/15 mL). Health worker cadre: recruitment for the study was done by an obstetrician and paediatric endocrinologist in the Kocaeli Maternity and Children Hospital outpatient obstetric clinics (Turkey, north of tropics). It was not stated who administered the supplements nor who measured the outcomes.
Outcomes	Maternal Primary Adverse event (hypercalcaemia) Infant Secondary Birthweight cord 25‐hydroxyvitamin D Laboratory method used for assessment of vitamin D concentrations: Enzyme immunoassay method (IDS ‐ Immunodiagnostic Systems)
Notes	• Start of supplementation:earliest at 13 weeks, latest at 32 • Pre‐gestational BMI (kg/m2): unknown/mixed; • Supplementation scheme/regimen: daily • Skin pigmentation based on Fitzpatrick skin tone chart (Fitzpatrick 1988): not available • Latitude: north of Tropics • Season at the start of pregnancy: spring Source of funding: not available Dates of the study: April 2011 – April 2012 Declarations of interest among primary researchers: this information is not reported by the trial authors
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Women were randomised using a simple randomisation method. Details on simple randomisation method used not provided.
Allocation concealment (selection bias)	Unclear risk	Not mentioned.
Blinding of participants and personnel (performance bias) All outcomes	High risk	This was an unblinded study.
Blinding of outcome assessment (detection bias) All outcomes	High risk	This was an unblinded study.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Data seems to have been reported for all participants who completed the study. G1:n = 28 (7 lost to follow‐up, 3 withdrawals, 4 could not be contacted); G2:n = 31 (7 lost to follow‐up, 4 withdrawals, 3 could not be contacted); G3:n = 32 (9 lost to follow‐up, 7 withdrawals, 2 could not be contacted).
Selective reporting (reporting bias)	Low risk	All intended outcomes (methods) were reported
Other bias	Unclear risk	There is insufficient information to allow judgement.