Vaziri 2016.

Methods	Randomised clinical trial.
Participants	169 pregnant women, both nulliparous and multiparous, aged 18 years or older, no history of mental illness and internal diseases such as hyper/hypothyroidism, no addiction to any kind of narcotic drugs or alcohol, not divorced or widowed, no pregnancy complications such as pre‐eclampsia, gestational diabetes, ruptured membranes and suspicion of preterm birth, no previous caesarean sections, with a live fetus singleton pregnancy, and gestational age of 26 to 28 weeks based on ultrasound results. who were under prenatal care in Hafez teaching hospital in Shiraz, Iran.
Interventions	Participants were assigned to 2 groups through block randomisation design: Group 1 (n = 78) received 2000 IU of vitamin D3 per day; and Group 2 (n = 75) received placebo. Both groups received their assigned treatments from 26 to 28 weeks of gestation until childbirth. Maternal serum 25‐hydroxyvitamin D concentrations were measured at baseline and childbirth. Besides, depression scores were evaluated 4 times: at 26 to 28 and 38 to 40 weeks of gestation, and finally at 4 and 8 weeks after birth. Participants were allowed to use prescribed supplementation outside this study’s protocol. Usually, pregnant women in Iran are prescribed iron and folic acid, which may be consumed as part of the multivitamin supplementation with 200–400 IU of vitamin D. They reported that 55 participants in the intervention and 69 in the control used other supplements but they did not provide the composition of the supplements. Health worker cadre: at first, a research team member who was responsible for data collection visited the prenatal care clinic of the hospital daily and based on the inclusion criteria, invited the mothers to participate in the study. The consumption of pills were assessed in later prenatal care visits and over the phone.
Outcomes	Maternal: baseline 25‐hydroxy vitamin D concentrations and at childbirth, depression score. Infant: vitamin D concentrations, anthropometric measurements of their infants at birth, 4th and 8th weeks of birth. Laboratory method used for assessment of vitamin D concentrations: Serum 25‐hydroxyvitamin D was measured with the Chemiluminescence immunoassay (CLIA) method.
Notes	Total dose of supplementary vitamin D during pregnancy: less than 56,000 IU; start of supplementation: 26 to 28 weeks of pregnancy; pre‐gestational BMI (kg/m2): unknown/mixed; supplementation scheme/regimen: daily; skin pigmentation based on Fitzpatrick skin tone chart (Fitzpatrick 1988): mixed/unknown; latitude: North of the Tropic of Cancer; season at the start of pregnancy: all year, from November 2014 to October 2015. Source of funding: the study was financially supported by a research grant from the Research Vice‐chancellor of Shiraz University of Medical Sciences. Dates of the study and location: November 2014 to October 2015, Iran. Declarations of interest among primary researchers (or state where this information is not reported by the trial authors): the authors declare that they have no competing interests.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Participants were randomised using a block randomisation design.
Allocation concealment (selection bias)	Unclear risk	The trial reported that it was a single‐blinded study, but it is not clear who was blinded and they did not report the allocation concealment. It is assumed that participants were blinded as the control group also received 2 pills, similar to the intervention group.
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	The trial reported that it was a single‐blinded study. However, data collection related to depression was done by a trained midwife outside the research team, who was blinded to group allocations but the rest of the assessments were not clear if they were performed by a blinded staff.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	The trial did not report if study staff conducting the assessments were blinded.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	143 women began study and 136 finished. Serum vit D checked for 130 women, but does not specify how many women were in each group.
Selective reporting (reporting bias)	Unclear risk	There is insufficient information to permit judgement.
Other bias	Low risk	The study appears to be free of other evident sources of bias.