Association between urine and serum estradiol levels in in vitro fertilization cycles.

To study the correlation between urine and serum estradiol (E2) controlled ovarian hyperstimulation (COH). This is a cross-sectional analytical study that was conducted in a tertiary care hospital. Seventy-seven urine and blood samplings were collected from infertile women who were treated with COH. An electrochemiluminescent immunoassay was performed to evaluate E2 levels between urine and serum samples on the 6th day and the day of ovarian trigger. In addition, the correlations were evaluated between urine E2 level and number of follicles, retrieved, metaphase II oocytes, and fertilization rate. A sub-analysis was performed for age, responding status and BMI. Seventy-seven infertile women were recruited. The medians of serum and urine E2 level levels on the day 6th of ovarian stimulation were 833.20 pg/ml (IQR; 516.90-1371.00) and 3.67 (IQR; 2.84-4.81), respectively. On the day of ovarian trigger, the median of serum E2 level was 2113.00 pg/ml (IQR; 1382.00-3885.00) and urine E2 level (E2/creatinine) was 6.84 (IQR; 5.34-8.70). The correlation between serum and urine E2 level on day 6th was 0.53 and the day of ovarian trigger was 0.59, p < 0.001. Moreover, the correlations of urine E2 level on the day of ovarian trigger to number of follicles, number of oocytes retrieved, metaphase II oocytes and fertilization rate were 0.57, 0.58, 0.61, and 0.64 (p < 0.001). The urine E2 level was moderately correlated to serum E2, number of follicles growth, oocytes retrieved and fertilization rate.