The UA is the channel for nutrient exchange between the fetus and the mother. Color Doppler ultrasound is typically used to check the blood flow of the fetal umbilical artery. The PI of the MCA is normally higher than that of the umbilical artery; however, when the umbilical blood flow resistance progressively increases, fetal hypoxia gradually increases, and a brain-sparing effect occurs, effectively redistributing oxygen and nutrients to vital organs (the brain, heart, and adrenal glands), manifested by increased blood flow in the MCA during systole, decreased PI and S/D ratios, even lower than the PI of cord blood flow, the PI of the MCA/UA—CPR < 1(3). When an abnormal increase in umbilical blood flow resistance is observed, the blood flow signal of the umbilical artery at the end of diastole decreases and even disappears (AEDF), leading to reflux (REDF). These occurrences and CPR < 1 are danger signs of intrauterine fetal death(9).
In clinical practice, CPR < 1 is a widely recognized danger sign of fetal hypoxia and intrauterine fetal death. If the aforementioned abnormalities are observed during umbilical blood flow monitoring and the fetus can survive in vitro, except for fetal malformations and chromosomal abnormalities, pregnancy is mostly actively terminated by cesarean section to free the fetus of poor intrauterine environment as soon as possible for in vitro treatment. In this study, patients in the immediately terminated pregnancy group had a longer gestational week when CPR < 1, with 34 weeks being the average. Considering the probability of fetal survival after birth and improved long-term prognosis, the patients opted for immediate termination of pregnancy. In the continuing pregnancy group, the gestational age when CPR < 1 occurred was relatively short, averaging 29 weeks only. Concerned about poor survival ability after birth, the patient chose to continue the pregnancy, waiting for an average of 3 weeks; beyond 33 weeks, pregnancy was terminated, although the newborn weight was still significantly lower than the average weight for the corresponding gestational age. After the occurrence of CPR < 1, the intrauterine environment of the fetus remained significantly poor, and the intrauterine growth rate was slow.
In the current study, the average gestational age when the umbilical blood flow resistance increased for the first time was 31.50 weeks; the average gestational age for the first occurrence of CPR < 1 was 32.52 weeks; and the average interval was 6.65 d. Therefore, after the umbilical blood flow resistance increased, color Doppler ultrasound was reviewed at least weekly to eventually determine the change in the umbilical blood flow. Intrauterine death was reported in 18 (40.9%) cases of continued pregnancy. The time of occurrence of fetal death in the uterus was 2–33 d after CPR < 1 was determined (average 12.8 d). Studies have shown that the time interval from inspection to AEDF to fetal death is 1–14 d, with an average of 6.3 d(10). Therefore, after determining CPR < 1 or AEDF in the umbilical blood flow and MCA blood flow is determined, attention should be directed toward strengthening monitoring to promptly detect abnormal fetal heart rates.
Studies have shown that CPR reduction is manifested before serious UA abnormalities occur(11). The current study indicates that CPR < 1 continued to develop AEDF in 14 cases, with an average interval of 8.8 d. AEDF progressed to CPR < 1 in only 3 cases. Moreover, when abnormal umbilical artery blood flow occurs, CPR < 1 is observed before AEDF in most patients. The TRUFFLE(12) study showed that in addition to minor changes in electronic fetal heart rate, the immediate termination of pregnancy is necessary, and the fetus showing FGR and abnormal umbilical artery blood flow waits until the venous catheter has an a-wave abnormality to terminate the pregnancy, which may provide an improved long-term outcome. In the current study, only 2 patients were monitored for abnormal a-wave venous catheters while waiting, but these patients suffered intrauterine death within a short period. Therefore, when a significant abnormality of the cord blood flow is detected, it is not appropriate to simply wait for the a-wave abnormality in the venous catheter to occur before terminating the pregnancy.
After treatment, 4 patients (9.1%) recovered to normal CPR and continued to monitor the normal cord blood flow until full-term delivery. Therefore, for cases with a fetus of very small gestational age and low birth weight, the survival ability of the newborn after birth and the long-term prognosis are extremely poor; thus, waiting is also a good choice.
Our study compared neonatal outcomes and found poorer outcomes in the group that continued pregnancy than in the group that terminated immediately .The main manifestations indicated that the incidence rates of neonatal asphyxia, neonatal pneumonia, neonatal sepsis, and neonatal anemia were significantly increased, and the incidence rates of neonatal respiratory distress syndrome and bronchopulmonary dysplasia were slightly increased in the continued pregnancy group relative to those in the immediately terminated pregnancy group.
The results of the current study are similar to those in the research conducted by Meher(4) and Flood(5). Their research results showed that the increase in umbilical artery blood flow resistance and blood flow redistribution might not completely achieve brain protection(4). Poor neonatal outcomes, decreased brain volume in neonates, and increased risk of adverse neurocognitive outcomes in children are related to fetal cerebral vasodilation(5). Neurodevelopmental disorders comprise a group of developmental disorders that occur during the developmental period and are often manifested before the child enters elementary school. Developmental disorders and defects lead to impaired personal social, academic, or professional functions. In the current study, motor developmental retardation was assessed using GMS, autism spectrum disorder was detected using M-CHAT, and child development was evaluated using the Gesell scale. Comprehensive assessment of sports, small sports, and social adaptability was also conducted. The aforementioned techniques were applied for the comprehensive assessment of neurodevelopmental disorders in children. The early prognosis of the two groups of children followed in this study showed that the incidence rates of autism spectrum disorder, motor development retardation, and growth retardation were slightly higher in the continued pregnancy group than in the immediately terminated pregnancy group, particularly those with autism spectrum disorder. The rate of neurodevelopmental disorders in children who continue to wait after CPR < 1 increased.
Analysis of pregnancy outcome and long-term prognosis of the children in each subgroup of the continued pregnancy group indicated that fetal intrauterine fetal death had a higher probability of occurrence in the patients with persistent CRP < 1 or patients who further developed AEDF. The incidence of adverse long-term outcomes was higher in children delivered by patients with persistent CRP < 1 than in the subgroup with normal CRP or CRP that briefly returned to normal during the monitoring period. Therefore, during monitoring of patients with abnormal blood flow in the umbilical artery, those with persistent CRP < 1 or those who further developed AEDF had poor prognosis and should actively terminate pregnancy.
Our study is limited to the loss of some patients to follow-up, which may lead to bias in research results.