Abstract: BACKGROUND: The impact of the endometrium’s structure and spiral artery blood flow parameters on the pregnancy rate of artificial insemination by husband remains unclear. This study identified the independent factors and constructed a prediction model with good clinical application efficacy after calibration of other confounding factors.
OBJECTIVE: To construct and validate a clinical pregnancy prediction model for artificial insemination by husband based on endometrial structure and uterine spiral artery blood flow parameters. 
METHODS: A retrospective analysis was conducted on 1 299 patients who underwent artificial insemination by husband treatment at Changzhou Maternal and Child Health Hospital from January 2017 to January 2021. The non-pregnancy group consisted of 1 182 patients, while the pregnancy group included 117 patients. Out of these patients, 93 cases were successfully matched between the pregnancy and non-pregnancy groups using a 1:1 propensity score matching method. Single-factor and multi-factor analyses were used to screen the endometrial structure and uterine spiral artery blood flow parameters to determine their influence on artificial insemination by husband outcomes. The optimal cutoff value was established for each independent influencing factor through receiver operating curve analysis and their risk trend affecting artificial insemination by husband pregnancy outcomes was analyzed using a restricted cubic spline. The clinical efficacy of this combined forecast model was tested by using clinical decision curve and clinical influence curve methods.
RESULTS AND CONCLUSION: (1) There was no statistical significance in non-endometrial factors between the pregnancy group and the non-pregnancy group, and the data had a good balance by propensity score matching (P > 0.05). (2) Single-factor analysis identified several subendometrial parameters as significant influencing factors of artificial insemination by husband pregnancy outcomes, including vascularization index, flow index, vascular flow index, resistance index, pulsatility index, maximum systolic velocity/end-diastolic velocity, thickness of average junction zone and maximum junction zone from the basal endometrium to the outer myometrium inner layer (P < 0.05). (3) Multivariate logistic regression analysis revealed that thickness of average junction zone, pulsatility index, and vascular flow index were independent influencing factors of pregnancy outcomes of artificial insemination by husband, vascular flow index > thickness of average junction zone > pulsatility index. (4) Receiver operating characteristic curve analysis indicated that the area under receiver operating characteristic curve of vascular flow index was 0.704 (0.629, 0.779), and the optimal cutoff value was 6.26; the area under receiver operating characteristic curve of thickness of average junction zone was 0.660 (0.582, 0.739), and the optimal cutoff value was 6.38; the area under receiver operating characteristic curve of pulsatility index was 0.642 (0.563, 0.721), and the optimal cutoff value was 1.18. (5) The restricted cubic spline analysis revealed that artificial insemination by husband pregnancy outcomes were significantly positively affected when the vascular flow index was > 6.24 or the thickness of average junction zone was ≤6.55 mm, while a negative risk was associated with pulsatility index > 1.27. (6) The clinical decision curve and clinical influence curve analyses exhibited that the combined prediction model had the maximum clinical net benefit at the threshold probability value of 0.17-0.93, and the ratio of loss to benefit was consistently less than 1 in the threshold probability range, indicating that the model had good clinical efficacy. (7) It is concluded that after adjusting for other confounding factors outside of the endometrium using propensity score matching and multifactorial logistic regression, the thickness of average junction zone, pulsatility index and vascular flow index were independent factors that influenced pregnancy outcomes of artificial insemination by husband. Through determining their optimal cutoff values and assessing their risk trends, it was confirmed that the combined prediction model had good predictive value and clinical efficacy. 

Key words: three-dimensional ultrasonic testing, endometrial structure, uterine spiral artery blood flow parameter, artificial insemination by husband, prediction model