Change in fetal heart rate

Introduction The fetal heart rate is the curve of the fetal heart rate regulated by the sympathetic and parasympathetic nerves. The curve of the monitoring pattern formed by the instantaneous fetal heart rate changes can be used to understand the fetal heart reaction during fetal movement and contractions. No oxygen deficiency. Abnormal fetal heart rate in most cases means that the fetus has hypoxia in the uterus. The more severe the abnormal fetal heart rate, the more severe the fetal hypoxia is, but not all fetal heart abnormalities are caused by hypoxia. In addition, the condition of the pregnant woman itself also affects the changes in the fetal heart, such as a fever in pregnant women.

Cause

1. Maternal factors: Insufficient oxygen content in maternal blood is an important cause. There is no obvious symptom in the mother during mild hypoxia, but it will affect the fetus. The maternal factors that cause fetal hypoxia are:

(1) Insufficient blood supply to small arteries: such as hypertension, chronic nephritis and pregnancy-induced hypertension.

(2) Insufficient oxygen carrying capacity of red blood cells: such as severe anemia, heart disease, heart failure and pulmonary heart disease.

(3) Acute blood loss: such as prenatal bleeding disorders and trauma.

(4) uterus placental blood supply obstruction: emergency or uterine inconsistent contraction: improper use of oxytocin, causing excessive contractions; prolonged labor, especially the second stage of labor extension; excessive uterine expansion, such as polyhydramnios and multiple births Pregnancy; premature rupture of membranes, umbilical cord may be stressed.

2, fetal factors

(1) Fetal cardiovascular system dysfunction, such as intracranial hemorrhage of severe congenital cardiovascular disease.

(2) Fetal malformation.

3, umbilical cord, placental factors: umbilical cord and placenta are the transmission and transmission channels of oxygen and nutrients between the mother and the fetus, and its dysfunction will inevitably affect the fetus's inability to obtain the required oxygen and nutrients.

(1) cord blood transport is blocked

(2) Low placental function: such as expired pregnancy, placental development disorder (too small or too large), abnormal placental shape (membranous placenta, contoured placenta, etc.) and placental infection.

an examination

Related inspection

Fetal heart monitoring amniotic fluid color

1. Diagnosis of chronic fetal distress

(1) placental function test: determine the 24-hour urine E3 value and observe continuously, if the acute aggregation is reduced by 30% to 40%, or in the end of pregnancy, the 24-hour urine E3 value is below 10mg, indicating fetal placental function. Decrease.

(2) Fetal heart monitoring: Continuously describe the fetal heart rate of pregnant women for 20 to 40 minutes, and the normal fetal heart rate baseline is 120 to 160 beats/min. If the fetal heart rate is not accelerated at the time of fetal movement, the baseline variability is <3 times/min, suggesting fetal distress.

(3) Fetal movement count: When the pregnancy is near full term, the fetal movement is >20 times/24 hours. The calculation method can detect the number of fetal movements for each hour in the early, middle and late pregnancy, and multiply the number of fetal movements by 3 times, which is the number of fetal movements close to 12 hours. Fetal movement reduction is an important indicator of fetal distress, and daily monitoring of fetal movement can predict the safety of the fetus. After the fetal movement disappears, the fetal heart will disappear within 24 hours, so you should pay attention to this point so as not to delay the rescue opportunity. Excessive fetal movement is often a precursor to the disappearance of fetal movement, and should also be taken seriously.

(4) amniocentesis: see amniotic fluid turbid yellow stained to dark brown, which helps the diagnosis of fetal distress.

2, the diagnosis of acute fetal distress

(1) fetal heart rate change: fetal heart rate is an important sign to understand whether the fetus is normal: 1 fetal heart rate > 160 beats / min, especially > 180 beats / min, for the initial performance of fetal hypoxia (pregnant heart rate is not fast 2 cases of fetal heart rate <120 beats / min, especially > 100 beats / min, for fetal risk; 3 late fetal heart rate deceleration, variability deceleration or (and) baseline lack of variation, all indicate fetal distress. When the fetal heart rate is abnormal, the cause should be examined in detail. Fetal heart rate changes can not be determined by only one auscultation. Multiple examinations should be performed and the position should be changed to the lateral position for a few minutes.

(2) Amniotic fluid meconium contamination: fetal hypoxia, causing vagus nerve excitement, intestinal peristalsis, anal sphincter relaxation, so that meconium is discharged into amniotic fluid, amniotic fluid is green, yellow-green, and then turbid brownish yellow, that is, amniotic fluid I Degree, II degree, III degree pollution. After the membrane is broken, the amniotic fluid flows out, and the characteristics of the amniotic fluid can be directly observed. If the membrane is not ruptured, it can be seen through the amniotic membrane and through the membrane to understand the characteristics of amniotic fluid. If the first exposed part of the tire is fixed, the former sheep's water sac can reflect the difference between the amniotic fluid and the amniotic fluid. If the anterior amniotic fluid sac is clear and the fetal heart rate is not normal, if the rupture of the membrane can be broken according to the situation, the scallops can be slightly lifted up after disinfection. The amniotic fluid above it can understand the water content of the lower part of the amniotic cavity. .

Amniotic fluid I degree, even II degree pollution, fetal heart rate is always good, should continue to closely monitor fetal heart rate, not necessarily fetal distress, amniotic fluid III degree polluters, should end early delivery, even if the newborn Apgar score may be 7 points It should also be vigilant because of the high chance of newborns. Mild contamination of amniotic fluid, abnormal monitoring of fetal heart after about 10 minutes of monitoring, should still be diagnosed as fetal distress.

(3) Fetal movement: In the early stage of acute fetal distress, the first manifestation is fetal movement frequency, and then weakened and the number of times decreased, and then disappeared.

(4) Acidosis: After rupture of the membrane, the fetal scalp blood is examined for blood gas analysis. The indicators for diagnosing fetal distress are blood pH < 7.20, PO2 < 1.3 kPa (10 mm Hg), and PCO 2 > 8.0 kPa (60 mm Hg).

1, chronic fetal distress: more often in the end of pregnancy, often extended to labor and increased. The reason is mostly caused by maternal systemic diseases or pregnancy-induced diseases caused by placental insufficiency or fetal factors. Clinically, in addition to the presence of maternal disease causing insufficient blood supply to the placenta, intrauterine growth retardation occurs with prolonged fetal chronic hypoxia.

2, acute fetal distress: mainly occurs during childbirth, mostly due to umbilical factors (such as prolapse, around the neck, knotting, etc.), placental abruption, excessive contractions and long duration and maternal low blood pressure, shock, etc. Caused. Clinical manifestations in fetal heart rate changes, amniotic fluid meconium contamination, fetal movement frequency, fetal movement disappeared and acidosis.

Differential diagnosis

Abnormal fetal heart rate: fetal heart rate is regulated by sympathetic and parasympathetic nerves. The curve of the monitoring pattern formed by the instantaneous fetal heart rate changes can be used to understand the fetal heart reaction during fetal movement and contractions. No oxygen deficiency.

Normal pregnancy is performed once a week from the 37th week of pregnancy. If there are complications or complications, you can start from the 28th to 30th week of pregnancy. Should pay attention to whether the rhythm of fetal heart sounds is slow or slow, etc., normal fetal heart sounds 120 ~ 160 beats / min, if the fetal heart sounds 160 beats / min or more or last 100 beats / min mean fetal intrauterine hypoxia, should Timely treatment.

Sinus fetal heart rate: Fetal heart rate is sinusoidal Fetal Heart Rate (SFHR). Many authors believe that the appearance of SFHR indicates that the fetus has serious danger and is a sign of fetal dying. The mortality rate of infants is as high as 50% to 75%.

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