Aim:
Background: Infertility is a common health problem in our community. Despite the large number of articles published annually about infertility in Iraq, there is no large national population-based study to figure out the exact prevalence of infertility in Iraq. However, the prevalence rate of infertility globally is in the range of 8% to 12%. A low level of vitamin D is linked to insulin resistance and other problems of PCOS including fertility. Aim of study: the current study was planned and conducted aiming at exploring the role of vitamin D supplementation in PCOS women who failed to ovulation induction by letrozole in previous trials.

Material and methods:
Patients and methods: The study included 30 women diagnosed with PCOS and were complaining from primary infertility. Those women were treated previously for 3 months with letrozole aiming at inducing ovulation, but there was failure of response to treatment. Those 30 women were selected from a pool of women who were evaluated for serum vitamin D and were proved to have vitamin D deficiency (<20 ng/ml).

Results:
Results: Daily monitory for ovulation by transvaginal ultrasound was done staring from day 7 till day 25 of the cycle. The main outcomes were the number and the size of follicles. In addition, they were followed up for evidence of pregnancy using biochemical serum and urine examination.

Conclusions:
Conclusion: When women with polycystic ovarian syndrome are treated with letrozole, vitamin D supplementation enhances both the result of ovulation induction and pregnancy.