Clinical Application of Fetal Umbilical Vein Doppler Parameters in Maternal Preeclampsia

Objective: To observe the changes of fetal umbilical vein (UV) Doppler parameters in pregnant women with preeclampsia (PE) and analyze their pre-dictive values for maternal PE. Methods: Forty-six patients with PE who underwent systematic ultrasound examination in our hospital from December 2017 to May 2021 were included as the subjects, which were divided into two groups according to the severity of the disease (23 cases in each group). And 120 normal pregnant women who underwent health examination in our hospital during the same period were enrolled as the control group. Color Doppler ultrasonography was used to monitor the umbilical vein flow (QUV), left portal vein flow (QLPV), venous catheter flow (QDV), left portal vein (LPV) shunt rate and venous catheter (DV) shunt rate. And the sensitivity and specificity of the related indexes were calculated and analyzed according to the gold standard for clinical diagnosis of PE. Results: As the severity of PE increased, the fetal QUV, QLPV and LPV shunt rates decreased, and the QDV and DV shunt rates increased, with statistically significant differences compared with the control group (P < 0.05). The specificity and sensitivity of the combination of fetal QUV, QLPV, QDV, LPV shunt rate and DV shunt rate in predicting PE were higher than those of the indexes used alone (P < 0.05). Conclusion: The fetal umbilical vein Doppler parameters QUV, QLPV, QDV, LPV shunt rate, and DV shunt rate have some value in predicting PE, but their combination showed greater value, as well as higher diagnostic and clinical significance.

the umbilical vein is the only oxygen supply pathway to the fetus, along with the increase of gestational weeks, the fetal oxygen demand will increase due to the needs of fetal growth and development, and its blood flow will increase accordingly. In contrast, patients with PE have abnormal blood perfusion to the placenta due to suppressed trophoblast infiltration, impaired spiral artery remodeling, vasospasm and placental vascular endothelial cell dysfunction [3]. When the fetus is exposed to inadequate blood and oxygen supply to the uteroplacenta, some hemodynamic changes occur in the umbilical venous circulation to counteract the inadequate oxygen supply [4]. In this study, we analyzed the efficacy of fetal umbilical vein Doppler parameters in the prediction of PE through a controlled clinical study, which is reported below.

General Data
Forty-six patients with PE who were treated in the obstetrics department of our hospital from December 2017 to May 2021 were selected for the study, and were divided into mild and severe groups based on the degree of PE, with 23 cases in each group. The gestational weeks at the time of the proposed initial diagnosis were between 16 -20 weeks. Inclusion criteria: 1) all had regular antenatal checkups at our hospital; 2) 18 -35 years old with ≥20 weeks of gestational cycle; 3) intrauterine singleton pregnancy; 4) meeting the diagnostic criteria and severity classification criteria of PE [5]. Mild: blood pressure ≥ 140/90mmHg combined with proteinuria > 300 mg/24h, may be accompanied by headache and abdominal discomfort; severe: blood pressure ≥160/110mmHg, proteinuria > 2 g/24h, blood creatinine > 106 μmol, oliguria. 5) All were delivered of a baby in our hospital. Exclusion criteria: a) combined with other high-risk pregnancy factors, such as age, diabetes mellitus, birth canal abnormalities, previous history of adverse pregnancy and delivery; b) fetal malformations; c) incomplete clinical data. One hundred and twenty healthy pregnant women who were registered at the obstetrics department of our hospital and received regular prenatal checkups during the same period were used as the control group, all of whom were free of chronic hypertension, anemia and other cardiovascular diseases. was measured, and then the LPV shunt rate and DV shunt rate were calculated.

Comparison of Basic Clinical Conditions of Pregnant Women between Groups
The analysis of clinical data showed that there was no significant difference in age, pre-pregnancy body mass index (BMI), gestational week of examination, pregnancy and delivery between PE mild group, PE severe group, and the control group, with no statistical significance (P > 0.05). The detailed results are shown in Table 1.

Comparison of Fetal Umbilical Vein Circulation Doppler Parameters between Groups
The results of clinical Doppler examination showed that in the PE group, the fetal QUV, QLPV and LPV shunt rates were lower than those in the control group, while the QDV and DV shunt rates were higher than those in the control group.
Both of the mild and severe PE groups showed statistically significant differences, compared with the normal control group (P < 0.05). As the severity of PE increased, the fetal QUV, QLPV and LPV shunt rates were lower, while the shunt rates of QDV and DV were higher in the severe group, compared with the mild group, all with statistical significance (P < 0.05). The results are shown in Table 2.

Discussion
PE is a disease specific to pregnancy with a prevalence of about 5% -10% [8].
Clinical manifestations are hypertension, proteinuria or other multisystem abnormalities after 20 weeks of gestation. The condition is an important contributor to maternal and fetal morbidity and mortality [9]. Therefore, early prediction, early intervention and timely monitoring of PE are particularly important.
With the continuous innovation and development of color Doppler ultrasound diagnostic technology, its role in prenatal diagnosis is increasing. Due to its many advantages over other examinations [10], such that it is safe, noninvasive, accurate, reproducible, and can reflect the blood supply of tissues and organs in real time, it has been used in the evaluation of PE [11].
At present, the clinical pathogenesis of PE is not fully clarified, but it has been widely recognized clinically that the placenta is a key factor in the pathogenesis of PE [12]. Decreased trophoblast infiltration capacity in the placenta of PE, shallow placental implantation, and impaired uterine spiral artery remodeling lead to decreased vascular production in the placenta and ultimately to inadequate placental perfusion. When the placenta is undersupplied with blood and oxygen, changes in hormone levels in the body contribute to an increase in the internal diameter of the DV, which leads to an increase in DV shunting, while extensive constriction of the intrahepatic portal system occurs, and UV blood is redistributed, preferentially flowing through the venous catheter away from the liver and towards the heart, reaching the coronary arteries and cerebral circulation, etc., which facilitates the nutrition and oxygen requirements of vital organs [13]. The umbilical vein is an important channel of fetal blood circulation, supplying highly oxygenated blood flow from the placenta to the fetus, and is responsible for obtaining the nutrients required for fetal growth and development. During normal pregnancy, along with the maturation of the placenta, the placental vessels gradually thicken, the vascular resistance decreases, and the ventricular compliance also increases with the decrease of cardiac after load, which results in the decrease of end-diastolic pressure and the increase of systolic return flow rate; meanwhile, the internal diameter of the DV increases gradually with the prolongation of the gestational week, and the UV blood flow increases accordingly. Thus, normal fetal UV blood flow parameters indicators increase with increasing gestational weeks. Based on this, the present study attempted to predict the occurrence of PE by detecting fetal UV blood circulation parameters, and then provide guidance and basis for early clinical intervention.
Clinical studies have found that umbilical vein blood flow predicts fetal growth restriction [14] [15] as well as infants younger than gestational age [16] and can be used as one of the indicators for fetal birth risk classification [17].
Because PE patients are less frequent clinically, they are often overlooked in clinical diagnosis, but they are significantly correlated with fetal prognosis, and analyzing the correlation between changes in UV circulatory Doppler parameters and different degrees of preeclampsia is a simple, noninvasive, reproducible and feasible method for predicting intrauterine distress and hypoxia, which is more sensitive and accurate than the currently used fetal monitoring, and it can quantify the amount of UV circulatory perfusion, promptly It is important to reduce the rate of perinatal disability and improve the quality of perinatal medicine and eugenics.
The results of this study showed that compared with the control group, fetuses in PE groups had significantly higher QDV and DV shunt rate, and significantly lower QUV, QLPV and LPV shunt rate. In addition, the severity of PE showed positive associations with QDV and DV shunt rate, and negative associations with QUV, QLPV and LPV shunt rate. In normal pregnancies, the effect of QUV on DV shunts is the greatest, because the placental hormonal effect thickens the umbilical vein, causing an increase in blood flow velocity and flow rate, which in turn increases the DV shunt rate. In addition, the specificity and sensitivity of the combined parameters of fetal QUV, QLPV, QDV, LPV shunt rate, and DV shunt rate in predicting PE were 95.40% and 98.15%, respectively, which were higher than those of single indicators (P < 0.05).

Conclusion
In conclusion, the fetal umbilical vein Doppler parameters QUV, QLPV, QDV, LPV shunt rate, and DV shunt rate change significantly in pregnant women with PE, which have some clinical significance in PE prediction. We found that the combination has higher clinical value, which can be used in clinical practice.