The observant expectant mother will find that there will be an extra "umbilical blood flow monitoring" during the ultrasound examination in the third trimester of pregnancy. So what is cord blood flow? What is the point of monitoring it?
Checking the cord blood flow is to determine the development of the fetus in the uterus, such as whether there is fetal growth retardation in the uterus, whether there is a tendency for pregnancy-induced hypertension, and whether there is fetal hypoxia in the uterus.
In addition, fetal chromosomal abnormalities, congenital malformations and other umbilical cord blood flow can sometimes show abnormalities.
The normal value of cord blood flow is related to the number of weeks of pregnancy. There are three main items. The S/D value is the main indicator, and the S/D value in the third trimester is usually less than or equal to 3.0 as the normal value. Under normal circumstances, as the number of weeks of pregnancy increases, the S/D value gradually decreases.
PI: Umbilical artery blood flow pulsation index
RI: Umbilical artery blood flow resistance index
S/D: Umbilical artery blood flow peak-to-valley ratio
If the umbilical blood flow data is abnormal, it may be caused by the following reasons:
(1) Fetal malformation : Fetal congenital diseases are closely related to the resistance of the umbilical artery, and further B-ultrasound examinations are required.
(2) Abnormal umbilical cord: When the umbilical cord is entangled, too long or too short, or too thin and affects the placental circulation, the blood flow impedance index is abnormal. If the S/D value is higher than the normal value, and the B-ultrasound shows abnormal conditions such as the umbilical cord around the neck, it should be closely observed according to the stages of pregnancy.
(3) Poor placental dysfunction: Pathological changes of the placenta can reduce the placental volume, decrease the total effective blood vessel cross-sectional area, increase blood flow resistance, and decrease blood perfusion.
(4) Intrauterine growth retardation (IUGR): There are many reasons for the occurrence of IUGR in pregnant women. In addition to factors such as genetic nutrition, harmful exposure, deformity, and viruses, the proportion of IUGR caused by pregnancy appendages such as placenta is increasing. Large, manifested by increased S/D and RI values.
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