To investigate the relationship between maternal and fetal ultrasound parameters and pregnancy outcomes in pregnant women with a history of recurrent miscarriage (RSA) in the second and third trimesters of pregnancy and their efficacy in assessing the occurrence of adverse pregnancy outcomes (APOs).

From June 2022 to February 2024, we prospectively selected 61 pregnant women diagnosed with RSA who were seen at 25-31 weeks of pregnancy in the Department of Reproductive Medicine of Shenzhen Second People’s Hospital. We measured the pulsatility index (PI) and resistance index (RI) of the maternal bilateral uterine artery (UtA) and monitored the peak systolic flow velocity (PSV) and pulsatility index (PI) of the fetal middle cerebral artery (MCA) as well as the peak-systolic-velocity/end-diastolic-velocity (S/D) ratio, resistance index (RI), and PI of the fetal umbilical artery (UA). The mean pulsatility index (MPI) and mean resistance index (MRI) were derived by calculating the mean values of the UtA-PI and UtA-RI. We calculated the cerebroplacental ratio (CPR) according to the formula [CPR=MCA-PI/UA-PI]. We simultaneously measured the diameter (D) and time-averaged peak flow rate (TAmax) of the intra-abdominal umbilical vein (IUV) and the free loop of the umbilical vein (FUV), and calculated the umbilical vein blood flow (UVBF) according to the formula [Q=0.5TAmax×π×(D/2)²]. Pregnancy outcomes were followed, and the women were divided into either a normal pregnancy outcome group or an APO group. The correlation of maternal-fetal ultrasound parameters with APO was analysed, and their predictive value for APO was assessed.

Among the 61 pregnant women, 25 had APO. At 25-31 weeks of pregnancy, there were no statistically significant differences in fetal MCA-PSV, MCA-PI, UA-S/D ratio, UA-PI, UA-RI, IUV-TAmax, intra-abdominal umbilical vein blood flow (IUVBF), or FUV-TAmax between the two groups (P>0.05). Maternal UtA-MPI and UtA-MRI, as well as fetal IUV-D, FUV-D and FUVBF, were significantly higher in women with APO compared to those with normal pregnancy outcomes (0.85±0.24 vs 0.71±0.16, 0.53±0.09 vs 0.48±0.07, 0.50 [0.45, 0.54] vs 0.47 [0.43, 0.51], 0.63±0.07 vs 0.57±0.06, and 159.92±48.38 vs 131.41±38.40, respectively; P<0.05). Lasso regression was employed to identify three predictors of APO, which were IUV-D, FUV-D, and UtA-MPI. The AUC for the above three indexes to predict APO was 0.653, 0.718, and 0.666, respectively; the AUC of their combination was 0.839, with a sensitivity of 64.0% and specificity of 97.2%.

Maternal UtA-MPI and UtA-MPI, as well as fetal IUV-D, FUV-D, and FUVBF at 25-31 weeks of gestation in patients with RSA are associated with pregnancy outcomes. IUV-D, FUV-D, and UtA-MPI are important predictors of APO, and the combination of them has better predictive efficacy, which is clinically valuable in guiding high-risk pregnancies.