This study is a single center retrospective study.
1. Patients
We summarized 38 cases of hyper-coiling umbilical cord diagnosed in our hospital from January 2019 to March 2021 whose UCI was more than 0.60, except for severe obstetric complications such as preeclampsia, gestational diabetes mellitus (GDM), twin pregnancy, pregnancy with immune system diseases, viral infection, fetal chromosomal abnormalities or structural malformations and fetal distress caused by other reasons. Finally, 29 patients with hyper-coiling umbilical cord without other complications were retained. And all patients conformed hyper-coiling umbilical cord after birth by measured UCI.
2. Ultrasound examination
The routine fetal ultrasound scan was performed following the practice guidelines of the International Society of Ultrasound in Obstetrics and Gynecology [5], using a Voluson E8 Expert machine (GE Healthcare, Kretzchnik). The growth and development parameters (including biparietal diameter, head circumference, abdominal circumference, and femur length. i.c. BPD, HC, AC, FL), amniotic fluid volume, placental position, umbilical cord, and its attachment point were recorded.
3. Classification of hyper-coiling umbilical cord
We would measure the UCI of suspected hyper-coiling umbilical cord patients and record. When UCI > 0.60, it can be diagnosed as the hyper-coiling umbilical cord. Then the following examinations were performed according to the routine of our hospital. Whether combined or not one of the following 6 high-risk factors, patients were divided into the complex and simple hyper-coiling umbilical cord. After that regular ultrasound reexamination was conducted in our hospital every 2~4 weeks. Once diagnosed as hyper-coiling umbilical cord patients, the current and subsequent ultrasound reviews were completed by two fixed obstetric ultrasound experts.
① Measured the blood flow spectrum of the umbilical artery on one or both sides of the fetal bladder. According to the spectrum shape, the umbilical artery was defined as high resistance type and normal type. High resistance type referred to the blood flow spectrum of one or both sides of the umbilical artery, which shows that notch in the early diastolic period and the blood flow velocity increases rapidly in the diastolic period, and none of the above-mentioned was normal(Figure 1)
② To determine whether there was intrauterine growth restriction (FGR), the FGR was used to describe fetuses with an estimated fetal weight less than the 10th percentile for gestational age [6].
③ Measured the peak flow velocity of the middle cerebral artery during the diastolic period, and it is defined as faster if bigger than 1.5MoM. The increased peak flow during the diastolic period means the adverse state of fetal hypoxia, which is different from that in systolic period means fetal anemia.
④ Amniotic fluid index( AFI) < 5cm was used to diagnose oligohydramnios.
⑤ The echo of brain parenchyma was enhanced.
⑥ The spectrum of venous catheter(VC) blood flow was defined as abnormal when there was a reverse A wave.
4. Pregnancy outcome and follow-up
According to the delivery situation, the patients were divided into three groups. The patients with severe fetal abnormalities or intrauterine fetal death were terminated pregnancy group; The patients with fetal distress due to abnormal fetal heart rate monitoring and termination of pregnancy by emergency cesarean section were divided into intervention group [7] [8]; The patients with normal fetal heart rate monitoring and no fetal distress were selected as non-intervention group. Reviewed and summarized the prenatal and intrapartum fetal heart rate monitoring, gestational age at delivery, mode of delivery, and neonatal birth weight of the three groups. The birth weight of the newborn was less than the tenth percentile considered to be small for gestational age (SGA). The neonatal growth and development were followed up by telephone.
5. Statistical methods and the feasibility of establishing HC clinical early warning system
We used SPSS 22.0 software to analyze the data. The measurement data of normal distribution were expressed by means ± standard, compared the results by t-test, and the rank-sum test was used for measurement data of non-normal distribution. The counting data were expressed by frequency and was adopted by χ 2 inspection. One-way ANOVA was used to compare the count data among the three groups, and the SNK-Q test was used to compare the mean of measurement data. All the statistical tests were used a two-sided test, P < 0.05 considered as a statistically significant difference.
Through the above statistical methods, the pregnancy outcomes of simple and complex HC patients were compared to see whether there were statistical differences. Compared the distribution of 6 ultrasound risk factors in terminated pregnancy group, intervention group, and non-intervention group. According to the statistical significance results in three groups, discussed the feasibility of establishing a clinical early warning system for HC patients.