Table. Characteristics of Included Randomized Clinical Trials.

Source	Country	Total Sample Size	Participants	Initiation and Timing of Supplementation	Interventions	Outcomes
Brooke et al,12 1980	United Kingdom	126	Pregnant Asian women	Third trimester	Ergocalciferol, 1000 IU/d, vs placebo	Cord blood 25(OH)D concentration, neonatal anthropometry, SGA, LBW, gestational age at birth, anthropometry at birth, 3, 6, 9, and 12 mo
Chawes et al,13 2016	Denmark	623	Pregnant women not after wk 26; without endocrine, cardiovascular, or nephrologic disorders; vitamin D3 intake no more than 600 IU/d	24 wk of gestation to 1 wk postpartum	Cholecalciferol, 2800 IU/d, vs 400 IU/d	Fetal or neonatal death, congenital malformation, admission to a NICU, preterm birth, wheeze, asthma, upper and lower respiratory tract infections, eczema, allergy skin prick test, allergy-specific IgE at age 3 y
Cooper et al,14 2016	United Kingdom	965	Pregnant women >18 y, singleton pregnancy, gestation <17 weeks, serum 25(OHD) level 10-40 ng/mL at 10-17 wk of gestation	14 wk of gestation or as soon as possible before 17 wk of gestation if recruited later until delivery	Cholecalciferol, 1000 IU/d, vs placebo	Fetal or neonatal death, congenital malformation, neonatal anthropometry, preterm birth
Dawodu et al,15 2013	United States	126	Arab expectant mothers, 12-16 wk of gestation, singleton pregnancy	12-16 wk of gestation until delivery	Cholecalciferol, 2000 or 4000 IU/d, vs 400 IU/d	Cord blood 25(OH)D concentration, SGA
Delvin et al,16 1986	France	30	Pregnant women	Third trimester	Cholecalciferol, 1000 IU/d, vs no treatment	Cord blood 25(OH)D concentration
Goldring et al,17 2013; Yu et al,36 2009	United Kingdom	179	Pregnant women	27 wk of gestation until delivery	Ergocalciferol, 800 IU/d, or cholecalciferol, 200 000 IU (1 dose), vs no treatment (control)	Fetal or neonatal death, cord blood 25(OH)D concentration, neonatal anthropometry, SGA, gestational age at birth, wheeze, eczema, upper and lower respiratory tract infections at age 3 y
Grant et al,18 2014	New Zealand	258	Pregnant women, 26-30 wk of gestation, singleton pregnancy, no vitamin D supplementation >200 IU/d, history of renal stones, hypercalcemia, or any serious pregnancy complication at enrollment	27 wk of gestation until delivery	Cholecalciferol, 1000 or 2000 IU/d, vs placebo	Fetal or neonatal death, cord blood 25(OH)D concentration, preterm birth, asthma, upper and lower respiratory tract infections, allergy skin prick test, allergy-specific IgE at age 3 y
Hashemipour et al,19 2014	Iran	110	Iranian pregnant women with vitamin D deficiency	Start at 26-28 wk of gestation; duration, 8 wk	Cholecalciferol, 50 000 IU/wk, vs 400 IU/d	Fetal or neonatal death, cord blood 25(OH)D concentration, neonatal anthropometry, SGA, preterm birth
Hollis et al,20 2011	United States	350	Women with a singleton pregnancy	12-16 wk of gestation until delivery	Cholecalciferol, 2000 or 4000 IU/d, vs 400 IU/d	Fetal or neonatal death, admission to a NICU, cord blood 25(OH)D concentration, neonatal anthropometry, gestational age at birth
Hossain et al,21 2014	Pakistan	175	Women with singleton pregnancy	20 wk of gestation until delivery	Cholecalciferol, 4000 IU/d, vs routine care	Fetal or neonatal death, Apgar score, cord blood 25(OH)D concentration, neonatal anthropometry, SGA, gestational age at birth, preterm birth
Kalra et al,22 2012	Zimbabwe	109	Pregnant women	12-24 wk of gestation until delivery	Cholecalciferol, 120 000 IU (1 dose) or 60 000 IU (2 doses), vs standard care	Neonatal anthropometry, infant anthropometry at 3, 6, and 9 mo
Karamali et al,23 2015	Iran	60	Pregnant women prima gravida, aged 18-40 y, at risk for preeclampsia, without abnormal fetal anomaly scan	20-30 wk of gestation	Cholecalciferol, 50 000 IU/fortnight, vs placebo	Apgar score, neonatal anthropometry, LBW, gestational age at birth, preterm birth
Litonjua et al,24 2016	United States	835	Pregnant women aged 18-39 y; gestational age 10-18 wk; history of asthma, eczema, or allergic rhinitis; nonsmoker; English or Spanish speaking	10-18 wk of gestation until delivery	Cholecalciferol, 4400 vs 400 IU/d	Fetal or neonatal death, congenital malformation, admission to a NICU, cord blood 25(OH)D concentration, neonatal anthropometry, preterm birth, asthma, lower respiratory tract infections, eczema, allergy skin prick test, allergy-specific IgE at age 3 y
Mallet et al,25 1986	France	77	White pregnant women	7 mo of gestation	Ergocalciferol, 1000 IU/d or 200 000 IU (1 dose), vs control	Cord blood 25(OH)D concentration
March et al,26 2015	Canada	105	Pregnant women aged 18-45 y, healthy, 13-24 wk of gestation, exclusion of women receiving supplements >400 IU/d	13-24 wk of gestation until delivery	Cholecalciferol, 1000 or 2000 IU/d, vs 400 IU/d	Cord blood 25(OH)D concentration
Marya et al,27 1988	India	200	Pregnant women aged 22-35 y	7 mo of gestation	Cholecalciferol, 600 000 IU (2 doses), vs no supplementation	Neonatal anthropometry, LBW, gestational age at birth
Mojibian et al,28 2015	Iran	389	Pregnant women, 12-16 wk of gestation, serum 25(OH)D <30 ng/mL	12 wk of gestation until delivery	Cholecalciferol, 50 000 IU/fortnight, vs 400 IU/d	Apgar score, cord blood 25(OH)D concentration, neonatal anthropometry, LBW, preterm birth
Rodda et al,29 2015	Australia	45	Pregnant women, singleton pregnancy, serum 25(OH)D <30 ng/mL	12-16 wk of gestation until delivery	Cholecalciferol, 2000 IU/d (adjusted to 4000 IU/d if serum vitamin D level remains <75 nmol/L), vs standard care	Cord blood 25(OH)D concentration
Roth et al,30 2013	United States	147	Pregnant women	Third trimester	Cholecalciferol, 35 000 IU/wk, vs placebo	Fetal or neonatal death, 25(OH)D concentration, neonatal anthropometry, gestational age at birth, preterm birth, infant anthropometry at 12 mo, weight, length, and head circumference z scores in infants at age 1 y
Sablok et al,31 2015	India	165	Prima gravida with singleton pregnancy at 14-20 wk, without preexisting osteomalacia, known hyperparathyroidism, renal or liver dysfunction, tuberculosis, or sarcoidosis	20 wk of gestation until delivery	Cholecalciferol, 60 000 IU (1 dose), 120 000 IU (2 doses), or 120 000 IU (4 doses), vs no supplementation	Cord blood 25(OH)D concentration, neonatal anthropometry, SGA, preterm birth
Sahoo et al,32 2017	India	52	Pregnant women aged >18 y, singleton pregnancy, <20 wk of gestation, no known bone diseases or complicated pregnancy, no vitamin D supplementation within previous 3 mo	14-20 wk of gestation until delivery	Cholecalciferol, 60 000 IU/4 wk or 60 000 IU/8 wk, vs 400 IU/d	Cord blood 25(OH)D concentration, neonatal anthropometry, weight, length, and head circumference z scores in infants at age 1 y
Yap et al,33 2014	Australia	179	Women with singleton pregnancies, aged ≥18 y and gestational age <20 wk, no history of diabetes, calcium or vitamin D metabolism disorders, hypercalcemia, or significant renal impairment, no vitamin D supplements ≥1000 IU/d	20 wk of gestation until delivery	Cholecalciferol, 5000 IU/d, vs 400 IU/d	Fetal or neonatal death, cord blood 25(OH)D concentration, neonatal anthropometry, gestational age at birth, preterm birth
Yesiltepe Mutlu et al,34 2014	Turkey	51	Pregnant women aged >16 y, singleton pregnancy, no previously known calcium metabolism or untreated thyroid disorders	13-32 wk of gestation until delivery	Cholecalciferol, 1200 or 2000 IU/d, vs 600 IU/d	Neonatal anthropometry, neonatal 25(OH)D concentration
Zerofsky et al,35 2016	United States	49	Participants aged >18 y with a singleton pregnancy <20 wk	No later than 20 wk of gestation until delivery	Cholecalciferol, 2000 IU/d, vs 400 IU/d	Apgar score, neonatal anthropometry, gestational age at birth

Abbreviations: IgE, immunoglobulin E; LBW, low birth weight; NICU, neonatal intensive care unit; RCT, randomized clinical trial; SGA, small for gestational age; 25(OH)D, 25-hydroxyvitamin D.

SI conversion factor: To convert 25(OH)D to nanomoles per liter, multiply by 2.496.