Many people are not familiar with what umbilical cord blood flow is, although this term is not common, it is very important. Simply put, umbilical blood flow describes a condition of arterial constriction velocity, and changes in the value of umbilical blood flow velocity can be used to determine whether the fetus is developing well in the uterus. Next, we will explain what a low pi in umbilical blood flow represents.
A low pi in umbilical blood flow indicates that there are problems with pregnancy.
The normal value of umbilical blood flow at 24 weeks is 3.5 on average, with an upper limit of 4.25. Exceeding this value is considered abnormal. The pulsatility index (PI) is 1.12 ± 0.17, and the resistance index (RI) is 0.66 ± 0.07. After 30 weeks of pregnancy, fetal distress is more likely to occur when the umbilical artery's SV/DV3.0, PI1.7, and RI are 0.7.
The systolic peak value (A or S) and diastolic trough value (B or D) of arterial blood flow can be calculated to determine the S/D or A/B ratio, as well as the resistance index (RI=A-B/A) and pulsatility index (PI=A-B/mean A, B). During normal pregnancy, these values decrease with gestational age, usually A/B4 before 24 weeks, A/B less than 3.0 after 30 weeks, and RI less than 0.68.
The ratio of the maximum systolic blood flow velocity (S) to the end diastolic blood flow velocity (D) of the umbilical artery (S/D, A/B), and the dynamic changes in the S/D (A/B) ratio can be observed to determine the development of the placenta. Under normal circumstances, as the fetus develops, the placenta gradually enlarges. The vascular resistance gradually decreases, and the S/D (A/B) ratio gradually decreases. The S/D ratio almost linearly decreased from 2.8 to 2.2 from 25 to 41 weeks of pregnancy. Fetal intrauterine growth retardation, placental and fetal dysplasia, no enlargement of placenta, and no decrease in vascular resistance. Therefore, the S/D ratio does not decrease. In clinical practice, if the S/D ratio does not decrease regularly or instead increases, it indicates poor fetal development.
Pregnant women with low umbilical blood flow pi hope to have an understanding of the pi value of umbilical blood flow and what it represents after reading this article. This is very important. In order to promote the healthy growth of the fetus in the womb, pregnant women must promptly adjust the symptoms of low umbilical blood flow and restore normal umbilical blood flow as soon as possible.
