| objective Infertility has became a hot issue in the field of medicine and societies, and the main solution for this problem was in vitro fertilization(IVF). The relationship between vitamin D status and the result of IVF has been identified in some studies, but there is no proof with evidence-based medicine. We aimed to examine the association of vitamin D(25(OH)D) status in women and the result of IVF by conducting a meta-analysis and systematic review. Methods We searched in Embase, Cochrane, and Pubmed databases using two methods, including Medical Subject Heading(Me SH) terms and keywords terms using the following keywords:(’vitamin D’ or ’cholecalciferol’ or ’calcitriol’ or ’calciferol’ or ’ergocalciferol’ or ’25(OH)-D’ or ’1,25(OH)2 D3’) and(’in vitro fertilization’ or ’assisted reproduction technologies’). Meanwhile we identified the conference papers and included studies’ conferences using manual search. We searched cohort study, which explore the relationship between vitamin D level and in vitro fertilization. All articles were reviewed by two independent researchers according to including and excluding criteria, and we used the Newcastle–Ottawa Quality Assessment Scale(NOS) standards to evaluate the quality of studies, if a discrepancy was noted, we discussed or decided by the third one. Results data were summarized by Stata 12.0 software. We used the Q test and I2 statistic to detect the heterogeneity. P=0.10 was considered statistically significant, there was high heterogeneity in result when P<0.10, and there was low heterogeneity in result when P ≥ 0.10. I2=50% was considered statistically significant, and there was high heterogeneity in result when I2>50%. When P≥0.10 and I2<50%, the heterogeneity is low, and we used the fixed-effect model. When P<0.10, I2≥50%, the heterogeneity is high, and we used random-effect model to calculate combined effect size and 95%CI, and analyzed the course of heterogeneity. The funnel plot, begg test and egger test was used for evaluating the degree of publication bias. Results Our search resulted in the retrieval and screening of 131 studies. Of those, 9 studies met the eligibility criteria and included 6 studies in our meta-analysis finally. 25(OH)D<20ng/ml was associated with lower rate of clinic pregnancy(RR=0.80, 95%CI=0.67-0.96; P=0.32; I2=14.7%) and live birth rate( RR=0.76, 95%CI=0.61-0.93; P=0.54; I2=0.00%) than 25(OH)D≥20ng/ml in infertile woman with in vitro fertilization. There is no difference of clinic pregnancy rate(RR=0.78, 95%CI=0.56-1.10; P=0.048; I2=58.3%) and live birth rate(RR=0.78, 95%CI=0.578-1.053; P=0.196; I2=40.1%) between women with 25(OH)D<30ng/ml or≥30ng/ml. Serum and follicular fluid 25(OH)D have a positive association(r=0.54, 95%CI=0.45-0.63; P=0.432; I2=0.00%). It was not clear for the relationship between follicular fluid 25(OH)D and in vitro fertilization. Conclusions 1. Follicular fluid 25(OH)D level have a positive association with serum 25(OH)D in pregnant woman. 2. Lower 25(OH)D level(<20ng/ml) was related with lower clinic pregnancy rate and live birth rate in infertile women with in vitro fertilization. 3. Vitamin D insufficiency(25(OH)D<30ng/ml) was not related to lower clinic pregnancy rate and live birth rate, but this result was not stable. We should be cautious about the conclusion. |
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