To investigate the effect of cesarean scar defect and endometrial cavity fluid on the pregnancy outcomes of infertility patients with previous cesarean scar uterus undergoing in vitro fertilization-embryo transfer (IVF-ET).

This was a retrospective cohort study. Totally 732 cases of patients with previous cesarean scar uterus were selected from frozen-thawed embryo transfer (FET) cycles in the Fertility Center, Shenzhen Zhongshan Urology Hospital from January 2019 to March 2020. They were divided into four groups: group A (n=39) including patients with previous cesarean scar defect and without endometrial cavity fluid; group B (n=82) including patients with previous cesarean scar defect and with endometrial cavity fluid; group C (n=495) including patients without previous cesarean scar defect and without endometrial cavity fluid; group D (n=116) including patients without previous cesarean scar defect and with endometrial cavity fluid. The general data and pregnancy outcomes were compared among these groups. Multivariate logistics regression analysis of pregnancy outcome indexes was performed.

The transplantation age of group A was higher than that of group B [(38.33±3.55) years vs. (36.93±3.59) years, P=0.045], the endometrial thickness of luteal transformation day and the rate of good-quality embryo transplantation of group C were higher than those of group D [(9.40±1.56) mm vs. (9.03±1.59) mm, P=0.025; 75.76% (375/495) vs. 65.52% (76/116), P=0.024]. The egg retrieval age of group A was higher than that of group C [(37.72±3.55) years vs. (36.25±4.52) years, P=0.049], but the endometrial thickness of luteal transformation day was thinner [(8.74±1.58) mm vs. (9.40±1.56) mm, P=0.012], and the differences were statistically significant. The implantation rate, the biochemical pregnancy rate and the clinical pregnancy rate of group C were higher than those of group D [34.23% (230/672) vs. 22.58% (35/155), P=0.007; 48.28% (239/495) vs. 37.93% (44/116), P=0.044; 42.83% (212/495) vs. 30.17% (35/116), P=0.012]. The early abortion rate in group D was higher than that in group B [40.00% (14/35) vs. 17.24 % (5/29), P=0.047], the difference was statistically significant. Multivariate logistics regression analyses were used with adjustment for possible confounders: the maternal age at embryo transfer, the maternal age at egg retrieval, anti-Müllerian hormone (AMH),antral follicle count (AFC), basic follicle-stimulating hormone (FSH), endometrial CD138 results, FET protocol, and embryo attributes, the number of embryos transferred, embryo quality, the endometrial thickness and the progesterone value on the day of luteal transformation, the result showed that the implantation rate, the biochemical pregnancy rate and the clinical pregnancy rate of group D were lower than those of group C [22.58% (35/155) vs. 34.23% (230/672), P=0.006; 37.93% (44/116) vs. 48.28% (239/495), P=0.047; 30.17% (35/116) vs. 42.83% (212/495), P=0.022] and the differences were statistically significant. The implantation rate, the biochemical pregnancy rate and the clinical pregnancy rate of group B were higher than those of group D [29.52% (31/105) vs. 22.58% (35/155), P=0.049; 48.78% (40/82) vs. 37.93% (44/116), P=0.012; 35.37% (29/82) vs. 30.17% (35/116), P=0.030] and the differences were statistically significant.

Endometrial cavity fluid is the main factor that obviously affects the pregnancy outcome of infertility patients with previous cesarean scar uterus undergoing FET cycles.

Fertilization in vitro; Embryo transfer; Cesarean scar uterus; Cesarean scar defect; Endometrial cavity fluid; Pregnancy outcome