What Is Fetal Hypoxia?

Fetal signs of hypoxia in the uterus, endangering fetal health and life, is called fetal distress. Fetal distress is a syndrome and one of the main indications for cesarean section. Fetal distress occurs mainly during labor and can also occur during late pregnancy. Occurred in the labor process can be the continuation and exacerbation of late pregnancy. Fetal distress is more common in the prenatal period, and is mainly manifested by placental insufficiency. Pathophysiology of high-risk pregnancy, such as hypertension during pregnancy, chronic hypertension, nephritis, diabetes, heart disease, asthma, severe anemia, expired pregnancy, etc., or uterine blood loss due to vascular disease, or placental degeneration, or The blood oxygen concentration is too low, so that the fetus cannot get enough oxygen, which causes fetal growth retardation, erythrocytosis, reduced fetal movement, and even severe fetal distress, causing fetal death.

Basic Information

English name

fetal distress

Visiting department

Obstetrics and Gynecology

Common locations

Pregnant woman

Common causes

Insufficient oxygen content in maternal blood is an important cause; fetal cardiovascular system dysfunction, fetal malformation; umbilical cord blood flow is blocked, and placental function is low.

Common symptoms

The weight, uterine height, and abdominal circumference of a pregnant woman do not last or grow slowly. Fetal movement is reduced, less than 4 times / hour, and fetal heart rate acceleration is not obvious during fetal movement.

Causes of Fetal Distress

The etiology of fetal distress involves many aspects and can be grouped into three major categories.

Maternal factor

Insufficient oxygen content in maternal blood is an important reason. In mild hypoxia, the mother usually has no obvious symptoms, but it will affect the fetus. Maternal factors that cause fetal hypoxia include:

(1) Insufficient blood supply to the small arteries, such as hypertension, chronic nephritis and hypertension during pregnancy.

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

(3) Acute blood loss, such as prenatal hemorrhagic diseases and trauma.

(4) Obstructed uterine placental blood flow, rapid delivery or uncoordinated contraction of the uterus; improper use of oxytocin causes excessive contractions; prolonged labor, especially prolonged second labor; excessive swelling of the uterus, such as polyhydramnios and multiple pregnancy ; Premature rupture of membranes, umbilical cord may be compressed and so on.

2. Fetal factors

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

(2) Fetal malformations.

3. Umbilical cord and placenta factors

The umbilical cord and placenta are the transmission and transmission channels of oxygen and nutrients between the mother and the fetus. Their dysfunction will inevitably affect the fetus' inability to obtain the required oxygen and nutrients.

(1) Impaired cord blood flow.

(2) Insufficient placenta, such as post-pregnancy, placental dysplasia (too small or too large), abnormal placental shape (membrane placenta, contoured placenta, etc.) and placental infection.

Clinical manifestations of fetal distress

1. Pregnant woman's weight, uterine height, abdominal circumference does not last long or grows slowly.

2. Fetal movement monitoring

It shows that the fetal movement is reduced, especially when the fetal movement is less than 4 times / hour, pay attention to the possibility of fetal death.

3. Type B ultrasound system inspection

Fetal biparietal diameter, head-to-abdomen circumference ratio, femur length, and amniotic fluid volume indicate that there is fetal growth retardation.

4. Prenatal no stress test (nst)

Observe the fetal heart rate when the fetal movement is not accelerated, or no fetal movement, that is, non-responsive type. Sometimes spontaneous deceleration of fetal heart rate even occurs. The contraction stress test (cst) can be a positive result.

5. Comprehensive biophysical image scoring check

That is, fetal respiration, fetal movement, fetal tension, amniotic fluid volume measured by B-mode ultrasound, and nst test performed by fetal monitoring, can be characterized by low scores.

6. Placenta function check

It can measure estriol, placental lactogen, and estrogen / creatinine ratio, and it has a continuous low value or a decreasing trend.

7. Amnioscope

See amniotic fluid contaminated with meconium.

8. Chronic Fetal Distress

Occurs in the last trimester, often lasts to labor and worsens. The cause is mostly due to systemic or pregnant diseases caused by placental insufficiency or fetal factors. In addition to clinically found that the mother's presence of diseases causing insufficient blood supply to the placenta, fetal intrauterine growth retardation occurs with chronic fetal hypoxia.

9. Acute fetal distress

It mainly occurs during childbirth, mostly due to umbilical cord factors (such as prolapse, neck around, knotting, etc.), placental abruption, excessive contraction and long duration, and maternal hypotension and shock. The clinical manifestations were changes in fetal heart rate, contamination of amniotic fluid with meconium, frequent fetal movements, disappearance of fetal movements, and acidosis.

10. Fetal Heart Change

Abnormal changes in the fetal heart are the earliest symptoms of fetal distress. The normal heart rate of the fetus is 120-160 beats / min. Above 160 or less than 120 beats are abnormal. Less than 100 times indicate severe hypoxia. In distress, the fetal heart speeds up first, and the heartbeat is regular and strong. Later, the heartbeat begins to slow down, weaken, and the rhythm is irregular. However, it should be noted that when the uterus contracts, the blood circulation of the uterus-placenta is temporarily disturbed, which slows down the fetal heart, and when the uterine contraction stops, the fetal heart quickly returns to normal, so it should be between the two uterine contractions The fetal heart rate prevails.

11. Abnormal fetal movement

Fetal movement is one of the vital signs of the fetus, which can be used to understand the safety of the fetus in the uterus, and is also a good method for self-monitoring of pregnant women, with a reliability of more than 80%. Under normal circumstances, the fetal movement should be no less than 3 times per hour and no less than 30 times in 12 hours. If the fetal movement suddenly increases sharply and becomes frequent and intense after labor, it indicates that the fetus may have acute distress, most of which are caused by acute hypoxia caused by umbilical cord compression and placental abruption. If the number of fetal movements on that day is reduced by 30% or more than in the past, it means that the fetal movements are reduced. Once the fetal movement disappears, the fetus may die at any time. Most of the death time is 12 to 72 hours after the fetal movement disappears.

12. Amniotic fluid changes

When there is too little amniotic fluid, the contracted uterine wall can directly compress the fetus and umbilical cord, which is prone to fetal distress. When the uterine opening is wide after labor, if there is no tension in the anterior amniotic membrane, or there is no anterior amniotic membrane at all and the fetal membrane is close to the fetal head, or only a small amount of amniotic fluid flows out after the membrane is broken, or even no amniotic fluid outflow, it may indicate that there is too little amniotic fluid The problem. Under normal circumstances, amniotic fluid is a white transparent liquid. When the fetus is hypoxic, it excretes meconium and changes the color of the amniotic fluid. When giving birth in the head position, meconium and fetal heart abnormalities are the typical symptoms of fetal distress. The degree to which amniotic fluid is contaminated by meconium can be divided into three degrees. The amniotic fluid was pale green and thin when polluted. At the second degree of pollution, the amniotic fluid is green and thick, which can contaminate the fetal skin, mucous membranes and umbilical cord, and is mostly manifested by acute fetal hypoxia. At the third degree of pollution, amniotic fluid was mixed with a large number of yellow-brown feces, which was thick and had a small amount, which was a manifestation of fetal distress. The placenta, placenta, fetal skin and nails are stained yellow-brown, suggesting that the fetus has been hypoxic for more than 6 hours and is in a critical state.

Diagnosis of fetal distress

1. Diagnosis of chronic fetal distress

(1) Placental function test to determine 24-hour urine E3 value and dynamic continuous observation. If the rapid convergence decreases by 30% to 40%, or if the 24-hour urine E3 value is less than 10 mg continuously at the end of pregnancy, it indicates fetal placental function. Diminish.

(2) Monitoring of fetal heart rate Continuously describe the fetal heart rate of pregnant women for 20 to 40 minutes, and the baseline of normal fetal heart rate is 120 to 160 beats / min. If fetal heart rate acceleration is not significant during fetal movement, the baseline variability rate is <3 times / minute, suggesting the presence of fetal distress.

(3) Fetal movement count When the pregnancy is near term, the fetal movement is> 20 times / 24 hours. The calculation method can instruct pregnant women to monitor the number of fetal movements by 1 hour each morning, middle and night. The number of fetal movements of 3 times is multiplied by 4, 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 to avoid delaying the rescue time. Frequent fetal movement is often a precursor to the disappearance of fetal movement and should be paid attention to.

(4) Amniotic microscopy The opacity of amniotic fluid is yellow to dark brown, which is helpful for the diagnosis of fetal distress.

2. Diagnosis of Acute Fetal Distress

(1) Change in fetal heart rate Fetal heart rate is an important indicator to understand whether the fetus is normal: The fetal heart rate is> 160 beats / min, especially> 180 beats / min, which is the initial manifestation of fetal hypoxia (maternal heart rate is unpleasant) (Cases); fetal heart rate <120 beats / min, especially <100 beats / min, is a fetal danger sign; late fetal heart rate deceleration, mutation deceleration, or (and) lack of baseline variation, all indicate fetal distress. The cause of abnormal fetal heart rate needs to be checked in detail. The change of the fetal heart cannot be determined by only one auscultation. It should be checked several times and changed to the lateral position, and then the examination is continued for several minutes.

(2) Meconium pollution of amniotic fluid Fetal hypoxia causes excitement of the vagus nerve, hyperintestinal peristalsis, relaxation of anal sphincter, and excretion of meconium into amniotic fluid. Amniotic fluid is green, yellow-green, and then cloudy brownish yellow, that is, amniotic fluid degree, degree and degree pollution.

(3) Fetal movements In the early stage of acute fetal distress, the fetal movement first appeared as frequent fetal movements, and then became weaker and less frequently, and then disappeared.

(4) Acidosis After breaking the membrane, check the fetal scalp blood for blood gas analysis. The indicators for diagnosing fetal distress include blood pH <7.20, PO ₂ <1.3kPa (10mmHg), and PCO ₂ > 8.0kPa (60mmHg).

Fetal Distress Treatment

Chronic fetal distress

Should be based on the etiology, depending on the gestational week, fetal maturity and the severity of distress.

(1) Those who can be regular prenatal check-ups are expected to have a good fetal condition. Pregnant women should be rested in the lateral position to improve the placental blood supply and prolong the gestational weeks.

(2) It is difficult to improve the situation. It is close to full-term pregnancy. It is estimated that those who have a great chance of fetal survival after delivery can consider cesarean section.

(3) The farther from full-term pregnancy, the less likely the fetus will survive after childbirth. The situation should be explained to family members, and conservative treatment should be tried to extend the number of weeks of pregnancy. If the actual fetal placental function is not good, fetal development will be affected, so the prognosis is poor.

2. Acute fetal distress

(1) If the uterine opening is complete, the exposed part of the fetus has reached 3 cm below the level of the sciatic spine, and the fetus should be delivered via vagina as soon as possible.

(2) The cervix has not been fully expanded, and the fetal distress is not serious. Oxygen (mask supply) can be given to improve the blood oxygen supply of the fetus by increasing the blood oxygen content of the mother. At the same time, instruct the mother to lie on her left side and observe for 10 minutes. If the fetal heart rate becomes normal, continue observation. If the fetal heart rate is abnormally slowed due to the use of oxytocin, the infusion should be stopped immediately, and continue to observe whether it can return to normal. Urgent cases or those who fail to respond to the above-mentioned treatment should be immediately delivered by cesarean section.

Fetal Distress Prevention

Fetal distress can directly endanger fetal health and life. Therefore, regular prenatal checkups are very important to detect the occurrence of abnormalities in the mother or fetus in a timely manner, such as hypertension during pregnancy, chronic nephritis, expired pregnancy, placental aging, anemia, delayed fetal development, placenta previa, and heart disease. In order to determine the degree of harm to the fetus, formulate a corresponding treatment plan to prevent or treat it. Pay attention to self-care during pregnancy, increase nutrition, combine work with rest, avoid bad living habits, and prevent placental abruption. Consciously feel unwell, reduce fetal movement and seek medical treatment in a timely manner. Intrauterine distress for ineffective fetuses, if it is near term and not in labor, the extrauterine environment is better than intrauterine, and the pregnancy is terminated early.