Effects of serum estrogen levels before frozen-thawed blastocyst transfer on pregnancy outcomes in hormone replacement cycles

We investigated the effects of serum estrogen levels before frozen-thawed blastocyst transfer on pregnancy outcomes in hormone replacement cycles. Clinical data of 708 hormone replacement cycles with frozen-thawed blastocyst were retrospectively analyzed. According to quartile (P25) of serum estrogen levels on the endometrium transformation day, the 708 cycles were divided into group A(1) (E2 < 157.5 pg/ml), group A(2) (157.5 pg/ml ≤ E2 < 206.4 pg/ml), group A(3) (206.4 pg/ml ≤ E2 < 302.3 pg/ml) and group A(4) (E2 ≥ 302.3 pg/ml). According to quartile (P25) of serum estrogen levels on the frozen-thawed blastocyst transfer day, the 708 cycles were divided into group B(1) (E2 < 147 pg/ml), group B(2) (147 pg/ml ≤ E2 < 200.4 pg/ml), group B(3) (200.4 pg/ml ≤ E2 < 323 pg/ml) and group B(4) (E2 ≥ 323 pg/ml). According to different clinical outcomes, the 708 cycles were divided into clinical pregnant group and non-clinical pregnant group. The group A(4) (E2 ≥ 302.3 pg/ml on the endometrium transformation day) was significantly lower than other groups in blastocyst implantation rate and multiple-pregnancy rate (P < 0.05). The days of taking progynova was significantly different among groups on both endometrium transformation day and frozen-thawed blastocyst transfer day (P < 0.05), but there were no statistical differences in the mean age, endometrial thickness and number of high-quality blastocysts transferred among groups (P > 0.05). The mean age was significantly younger and the number of high-quality blastocysts transferred was significantly higher in the clinical pregnant group than in the non-clinical pregnant group (P < 0.05), but endometrial thickness, days of taking progynova, progesterone level on the blastocyst transfer day, and E2 level were not significantly different between both groups (P > 0.05). Multivariate regression analysis indicated that age was an independent factor affecting clinical pregnancy (P < 0.05). Correlation analysis displayed that the serum estrogen levels did not affect clinical pregnancy (P > 0.05). The days of taking progynova and serum estrogen levels before frozen-thawed blastocyst transfer do not affect pregnancy outcomes in hormone replacement cycles.