Table 1 main characteristics of the included studies

Abedi

2019

Iran

Double-Blind Randomized Placebo-Controlled Trial

13.6 ± 6.6/37.1 ± 7.7 vs 12.7 ± 6.4/14.4 ± 6.6

54

54

Vitamin D

placebo

ICSI

Infertile couples who had Vitamin D level below 30 ng/ml without symptom of Vitamin D deficiency

Six weeks

Aflatoonian

2014

Iran

Randomized controlled trial

below 30

57

57

Vitamin D

–

IVF/ICSI

Infertile women undergo IVF/ICSI

Six-eight weeks

Doryanizadeh

2021

Iran

Double-Blind Randomized Clinical Trial

27.5 ± 1.8 vs 27.6 ± 1.8

51

44

Calcitriol (Vitamin D3)

placebo

–

Infertile women

Four weeks

Espinola

2021

Italy

Randomized and controlled pilot study

25.4 (6.7; 16.0–40.0)/33.2(4.3; 23.3–40.4) vs 23.9 (4.9; 14.0–35.6) /24.3(5.2; 16.1–36.4)

60

60

Myo-Inositol (600 mg), folic acid (200 mg), melatonin (1.0 mg) and vitamin D3 (50 μg, 2000 IU) as cholecalciferol

Myo-Inositol (600 mg), folic Acid (200 mg), melatonin (1.0 mg), folic acid (200 μg)

–

Infertile women of different etiology

From the day of hCG administration until 14 days after embryo transfer

Fatemi

2017

Iran

Double-Blind Randomized Placebo-Controlled Trial

below 30

52

53

Vitamin E, 400 mg/day dl alpha tocopherylacetate and vitamin D3

placebo

ICSI

PCOS

Eight weeks

Kermack

2019

United Kingdom

Double-blinded randomized

controlled trial

74.33 ± vs 71.62 ± 24.69 nmol/L/ 154.63 ± 1.56 nmol/L vs. 68.50 ± 1.51

55

56

EPA(800 mg), DHA (1200 mg), or vitamin D in olive oil

Sunflower seed oil

IVF or IVF-ICSI

Women undergoing IVF

Six weeks

Lan

2018

China

Clinical trial

below 30

37

37

Vitamin D2

–

–

Infertile women who had failed to undergo IVF fresh embryo transplantation

Six weeks at least

Somigliana

2021

Italy

Randomized superiority double-blind placebo controlled clinical trial

20.0(15.5–23.6) vs 19.9(14.6–23.9)

308

322

Vitamin D3 diluted in olive oil

placebo (the olive oil)

Classical IVF and ICSI

Women undergoing IVF

A single administration

Tang

2017

China

Randomized controlled trial

–

235

155

Multivitamin tablets (elevit)pearl/daily orally

–

IVF-ET

Infertile women

Ninety days

Wdowiak

2020

Poland

Randomized controlled trial

–

50

50

600 mg MI, 200 μg folic acid, 1 mg melatonin, 50 μg equivalent to 2000 IU vitamin D3

placebo

ICSI

Infertile women

Three months

Zhao

2019

China

Clinical trial

–

190

115

25OH-VD

–

–

PCOS and insulin resistance

Two-three months

Zhuang

2019

China

Clinical trial

–

204

192

Vitamin D combined with metformin and clomiphene

metformin and clomiphene

–

Patients with PCOS combined with infertility

Three consecutive menstrual cycles

Abedi

50,000 units/week

300,000

Oral administration

18–38(31.9 ± 4.2/30.8 ± 4.4)

18–30(23.9 ± 2.1/23.8 ± 1.9)

77.4 ± 22.1/68.1 ± 19.3 months

–

–

Biochemical and clinical pregnancy rate

Aflatoonian

50,000/week

300,000-400,000

Oral administration

28.45 ± 3.74/29.56 ± 4.68

26.87 ± 1.77/26.29 ± 1.67

–

Frozen embryo transfer

Embryos A/B/C

Biochemical and clinical pregnancy rate

Doryanizadeh

Two 0.25 μg daily

560

Oral administration

20–40(32.5 ± 4.9/31.6 ± 4.9)

25.3 ± 3.2/24.9 ± 3.4

7.0 ± 4.7/7.1 ± 4.8 years

Frozen embryo transfer

–

Biochemical and clinical pregnancy rate, miscarriage rate and pregnancy continued until week 20

Espinola

50 μg, 2000 IU daily

42,000

Oral administration

≤ 42[34.7 (6.7;22–42)/35.9 (3.7;27.0–42.0)]

18.5–24.9[21.9 (2.1;17.6–28.4)/22.0 (2.3;17.6–27.5)]

3.7 (1.8;1.0–9.0)/3.6 (2.1;1.0–10.0) years

Fresh embryo transfer

Blastocysts graded A/B

Implantation rate, Biochemical and clinical pregnancy rate, miscarriage rate, multiple pregnancy rate

Fatemi

50,000 IU/one in two weeks-3300 IU/daily

200,000

Oral administration

18–38(28.07 ± 4.21/28.13 ± 3.73)

20–34(26.53 ± 2.99/26.13 ± 3.58)

61.61 ± 43.62/66.46 ± 36.31 months

Fresh and frozen embryo transfer

Embryo with good morphologic

Implantation rate, Biochemical and clinical pregnancy rate, multiple pregnancy rate

Kermack

10 μg, 400 IU daily

16,800

Oral administration

18–41(33.3 ± 4.1/33.4 ± 4.3)

18–32(24.3 ± 3.1/25.0 ± 3.9)

–

–

Embryo with highest

morphologic score

Implantation, clinical pregnancy and live bith rate

Lan

10 ml (50 mg)/one time in two weeks

45,000

Intramuscular injection

–

–

–

Frozen embryos

–

Implantation and clinical pregnancy rate

Somigliana

600,000 IU

600,000

Oral administration

18–39[35.0(32.0–37.0)/35.0(33.0–37.0)]

18–25[20.8(19.5–22.5)/21.1(19.7–22.9)]

3(2–4)/2.5(2–4) years

Fresh and frozen embryos

Blastocyst Stage (Day 5)

Biochemical and clinical pregnancy rate, miscarriage rate, multiple pregnancy rate and live birth rate

Tang

Vitamin D 500 IU/daily

45,000

Oral administration

24–43(32.5 ± 3.2)/23–42(31.8 ± 3.0)

–

1–12(4.2 ± 1.4)/1–11(4.0 ± 1.2) years

–

–

Clinical pregnancy, and miscarriage rate

Wdowiak

50 μg equivalent to 2000 IU vitamin D3 as cholecalciferol/daily

168,000

Oral administration

20–35(31 ± 3.11/31.2 ± 3.03)

24.76 ± 2.94/25.11 ± 2.39

–

–

–

Clinical pregnancy rate

Zhao

–

–

–

31.2 ± 4.3/32.1 ± 4.2,32.0 ± 3.4/31.6 ± 6.9

22.4 ± 2.4/24.7 ± 4.7, 23.5 ± 3.8/24.1 ± 4.4

3.8 ± 2.3/3.1 ± 3.2,3.7 ± 1.0/3.4 ± 2.2

Frozen embryos

–

Implantation and clinical pregnancy rate

Zhuang

3000 IU daily, 5 days/menstrual cycle

45,000

Oral administration

26.33 ± 4.05/25.64 ± 4.78

27.53 ± 4.13/27.28 ± 3.56

3.87 ± 2.44/3.52 ± 2.56

–

–

Pregnancy rate