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Table 1 Characteristic of studies included in our meta-analysis

From: Whether vitamin D was associated with clinical outcome after IVF/ICSI: a systematic review and meta-analysis

Studies Country Study design Protocol Sample size The time of sample collection Vd grouping criteria Outcome measures Main result Main confounding factors
Anifandis et al. 2010 [8] Greece Retrospective cohort study Short agonist protocol
IVF/ICIS
101 During oocyte retrieval < 20 ng/ml;
20.1-30 ng/ml;
> 30 ng/ml
Clinical pregnancy rate (CPR) Higher FF levels of 25(OH)D are associated with lower FF glucose levels and with lower CPR Age
BMI
Oocytes retrieved (n)
Rudick et al. 2012 [10] USA Retrospective cohort study Long agonist Flare-up
GnRH-ant IVF/ICSI
188 After hCG administration < 20 ng/ml;
20-30 ng/ml;
> 30 ng/ml
ou Opposite relation between 25(OH)D levels and IVF outcomes by race Age
BMI
Embryos transferred (n, quality)
Poor ovarian reserve
Firouzabadi et al. 2013 [14] Iran Prospective cohort study Long GnRH-a protocol
IVF
221 On the day of ovum pick-up < 10 ng/ml
10-29 ng/ml
30-100 ng/ml
CPR No significant association between FF or serum levels of 25(OH)D and CPR None
Garbedian et al. 2013 [9] USA Prospective cohort study Long GnRH-a
Flare-up
GnRH-ant
IVF
162 Before oocyte retrieval < 75 nmol/l
≥75 nmol/l
CPR High vitamin D level was related to higher CPR Age
BMI
Day 5[v. day3] embryo transfer
Fabris et al. 2014 [17] Spain Retrospective cohort study Egg donation recipients 267 After 2 weeks of HRT < 20 ng/ml;
20-30 ng/ml;
> 30 ng/ml
CPR;
Ongoing pregnancy rate
Low vitamin D level was not related to decreased CPR with egg donation. BMI
Paffoni et al. 2014 [12] Italy Prospective cohort study Long GnRH-a
Flare-up
GnRH-ant
IVF
335 Prior to to initiation of COH < 20 ng/ml;
≥20 ng/ml
CPR;
Implantation rate
High vitamin D level was related to higher CPR Race
BMI
Polyzos et al. 2014 [13] Belgium Retrospective cohort study Irrespective of the protocol
Single, blastocyst
IVF/ICSI
368 On the day of hCG administration < 20 ng/ml;
≥20 ng/ml
Chemical PR
CPR;
Live birth rate (LBR)
Low vitamin D level was related to lower clinical pregnancy rate and live birth rate Season of embryo transfer
Rudick et al. 2014 [11] USA Retrospective cohort study Egg donation recipients 99 At the time of down-regulation < 20 ng/ml;
20-30 ng/ml;
> 30 ng/ml
CPR;
LBR
Higher 25(OH)D levels associated with higher CPR and LBR Recipient age
Recipient BMI
Embryos transferred(n, quality)
Franasiak et al. 2015 [18] Canada Retrospective cohort study Long GnRH-a
Flare-up
GnRH-ant
FET/ICSI
517 On the day of ovulation trigger < 20 ng/ml;
20-30 ng/ml;
> 30 ng/ml
CPR
Ongoing PR
Vitamin D had no relationship with IVF outcomes Age
No. of embryo transferred
Race