When the umbilical cord is wrapped around the neck for one week and is loosely wound, it has no effect on the SD ratio. If the umbilical cord is compressed or wound too tightly, it may affect the changes of blood flow signals in the umbilical cord.
The SD value of umbilical cord blood flow refers to the ratio of systolic and diastolic umbilical arteries, which can reflect the blood supply and oxygenation of the fetus in the uterus, and help to assess the growth and development of the fetus.
When the umbilical cord is wrapped around the neck due to a change in fetal position, it has no effect on blood flow and the SD ratio is normal when it is loosely wrapped. However, if the umbilical cord is compressed or stretched, the umbilical cord blood flow is affected, which can cause the SD value to rise, suggesting that the resistance to blood flow is relatively high. At this time, it is necessary to closely monitor the fetal movement, fetal heartbeat changes, etc., in order to find out as early as possible whether there is fetal hypoxia, distress.
Clinically, 1/3 of fetuses can have umbilical cord bypass, but most of them will not cause fetal hypoxia. It is necessary to cooperate with the doctor to carry out ultrasound, fetal heart rate monitoring to assess whether the fetus is hypoxic. In addition, pregnant women need to learn to count the fetal movement and observe the fetal movement, if you find that the fetal movement is frequent or the decrease of fetal movement is obvious, you need to go to the hospital in time to consult the doctor.