Association Between Endometrial/Subendometrial Vasculature and Embryo Transfer Outcome: A Meta-analysis and Subgroup...

To examine the association between endometrial/subendometrial vasculature and in vitro fertilization-embryo transfer (IVF-ET) and frozen embryo transfer (FET) outcomes.

A meta-analysis of studies using endometrial/subendometrial 3-dimensional ultrasound and power Doppler angiography was performed to examine the vascularization index (VI), flow index (FI), and vascularization-flow index (VFI) in pregnant and nonpregnant women. Ten articles were analyzed, including 895 pregnant women and 882 nonpregnant women.

A subgroup analysis of the measuring time showed that the endometrial VI (standardized mean difference [SMD], 0.57; 95% confidence interval [CI], 0.40, 0.74; P < .00001), FI (SMD, 0.56; 95% CI, 0.33, 0.78; P < .00001), and VFI (SMD, 0.45; 95% CI, 0.28, 0.61; P < .00001) measured on the ET day, but not on the human chorionic gonadotropin (hCG) trigger day, were significantly higher in pregnant than nonpregnant women. Additionally, the subendometrial FI was significantly increased in pregnant women on the both hCG day (SMD, 0.68; 95% CI, 0.31, 1.06; P = .004) and ET day (SMD, 0.30; 95% CI, 0.08, 0.52; P = .007). A subgroup analysis of cycle type showed that the endometrial VI (SMD, 0.52; 95% CI, 0.30, 0.74; P < .00001), FI (SMD, 0.44; 95% CI, 0.22, 0.66; P = .0001), and VFI (SMD, 0.45; 95% CI, 0.23, 0.67; P = .03) on the ET day were significantly increased in pregnant women in the FET subgroup.

The subendometrial FI on the hCG day and endometrial VI, FI, and VFI on the ET day are potentially associated with pregnancy occurrence during IVF-ET. The endometrial VI, FI, and VFI could help identify appropriate timing for FET. However, the accuracy of these indices in predicting pregnancy occurrence must be further evaluated in additional large-scale studies.