Vitamin D improves in-vitro fertilization outcomes in infertile women with polycystic ovary syndrome and insulin resistance

BACKGROUND: The aim of f this study is to investigate the effect of vitamin D supplementation upon the outcome of in-vitro fertilization (IVF) in infertile women with polycystic ovarian syndrome (PCOS) and insulin resistance (IR). METHODS: Three hundred and five infertile patients with PCOS and insulin resistance undergoing IVF were included in this study. All participants underwent oral glucose tolerance test (OGTT). Insulin resistance was calculated by homeostasis model assessment. Vitamin D status was measured by assessing circulating levels of 25OH-VD in serum samples by radioimmunoassay. RESULTS: All the patients were then divided into four groups according to their relative levels of serum 25OH-VD (levels of 25OH-VD= 20 ng/mL were defined as being normal) and whether treatment had been administered prior to COH: Group I (deficiency group without treatment [25OH-VD< 20 ng/mL]); Group II (normal group [25OH-VD= 20 ng/mL]), Group III (normal group after treatment), Group IV (deficiency group after treatment). In total, 305 women were included in this study. Implantation rates across the four groups were 8.5% (9/106) in Group I, 49% (24/49) in Group II, 49.1% (55/112) in Group III and 14.3 (18/126) in Group IV, respectively. Clinical pregnancy rates were 19.3% (11/57), 65.2 (15/23), 66.7% (38/57) and 23.5% (16/68) in the four groups, respectively. Both the implantation rate and clinical pregnancy rate in groups in which serum 25OH-VD was normal (Groups II and III) were significantly higher (P<0.05) than the other two groups. Serum levels of 25OH-VD were highly correlated with clinical pregnancy and implantation rates (P<0.01). There also were significant differences among the four groups in terms of fertilization rate (80 +/- 16%, 93 +/- 10%, 90 +/- 12%, and 79 +/- 23%), two pronucleus (2PN) fertilization rate (59 +/- 21%, 72 +/- 14%, 76 +/- 17% and 66 +/- 24%) and cleavage rate (76 +/- 20%, 91 +/- 10%, 89 +/- 24% and 76 +/- 25%). Particularly marked differences were observed in the number of high-quality embryos (20 +/- 16%, 63 +/- 25%, 55 +/- 22%, and 32 +/- 19%) and the available embryos which could be transferred (2.5 +/- 1.8, 5.8 +/- 2.8, 5.2 +/- 2.4, and 3.6 +/- 1.9) (all P<0.01). Much higher rates of implantation and clinical pregnancy were observed among the 25OH-VD deficient patients who had received vitamin D supplements and 25OH-VD levels returned to normal compared to patients in which 25OH-VD levels did not return to normal. Group III, which had normal 25OH-VD levels following Vitamin D supplementation produced the same number of high-quality embryos as Group II which had normal 25OH-VD levels (Group III versus Group II; 7.6 +/- 4.1 vs. 10.6 +/- 5.2, 55 +/- 22% vs. 63 +/- 25%; P<0.05). CONCLUSIONS: Our data indicate that vitamin D supplementation can help return serum vitamin D levels in infertile women with PCOS and IR to normal levels leading to an improvement in the quality of embryos and a significantly higher clinical pregnancy rate. Maintaining a normal serum vitamin D level in PCOS women is very important in achieving a successful clinical pregnancy following in-vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI).