Meconium in amniotic fluid

Introduction In the course of labor, if meconium is found in amniotic fluid, the condition of the fetal heart must be carefully observed. If the fetal heart is also abnormal at the same time, the fetus is more likely to be inhibited due to hypoxia. Even if the fetal heart is normal, if the meconium in the amniotic fluid is more dark, when the amniotic fluid is meconium and thick, the fetus inhales such amniotic fluid into the lungs, prone to meconium aspiration pneumonia or more serious The situation causes fetal amniotic fluid and meconium aspiration syndrome, and it is necessary to terminate the pregnancy early. Amphoteric and amniotic fluid and meconium syndrome accounts for 0.3% to 2.0% of live births, and is more common in term infants and expired children. The main reason is that the fetus inhales amniotic fluid with meconium during birth, causing a series of symptoms such as suffocation and difficulty in breathing. Severe cases develop into respiratory failure or death. In the medical history, there are often fetal distress, prolonged labor, placental insufficiency, and dystocia. Amniotic fluid stained meconium is often a sign of fetal hypoxia, but full-term or expired children can have a small amount of physiological meconium discharged into amniotic fluid.

Cause

The cause of meconium in amniotic fluid:

Fetal hypoxia can cause group reflexes, discharge meconium, and spontaneous breathing, inhalation of meconium and amniotic fluid keratinocytes, thick inhalation of meconium can cause complete tracheal obstruction, atelectasis, acute asphyxia and hypoxia. Thin meconium amniotic fluid or inhaled amount can cause partial obstruction, causing sub-segmental atelectasis and obstructive emphysema. If the alveolar rupture can cause interstitial emphysema or pneumothorax. When the gas spreads along the vessel wall and lymphatic vessels to the mediastinum, it can cause mediastinal emphysema.

Meconium-stained amniotic fluid stimulates the respiratory mucosa or secondary infection can cause pneumonia. After entering the rehabilitation period, the inhaled matter is absorbed or swallowed, and severe cases form fibrosis, and emphysema and other lesions appear.

Meconium is contaminated throughout the body at birth. If the fetus is immersed in meconium and amniotic fluid for 4-6 hours, the nail can be dyed yellow-green. The umbilical cord, fetal fat, and placental amnion can be stained with meconium in 10-12 hours. Neonatal respiration is severely inhibited, with bradycardia, low muscle tone and shock. After spontaneous breathing, you can see shortness of breath, and gradually become difficult to breathe, intercostal depression and exhalation, and skin color. If the bruising is serious and the oxygen is not improved, the neonatal continuous pulmonary hypertension should be considered. The signs of the lungs are related to how much and how much feces are inhaled. If there is a pneumothorax, the breathing movements and breath sounds on both sides can be asymmetrical.

Cardiac malocclusion caused by severe asphyxia and hypoxia, right to left shunt, giant heart with peripheral circulatory congestion, occasionally convulsions. Blood gas analysis showed a decrease in PO2, an increase in Pco2 and a decrease in pH. Severe cases die within minutes to hours after birth, and the survivors have a prolonged course. The general case improved significantly within 2 days, and fully recovered after 10 days or more. In mild cases, dyspnea occurred only a few hours after birth. The X-ray examination showed slightly thickening of the lungs, mild emphysema, and mild diaphragmatic muscles. decline. In the case of more meconium inhalation, the two lungs may have dense patchy or nodular infiltration, the lungs are excessively inflated, occasionally a small amount of fluid in the chest, interstitial emphysema, mediastinal gas or pneumothorax.

an examination

Related inspection

Chest B super chest MRI chest perspective chest CT examination

Examination and diagnosis of meconium in amniotic fluid:

(1) Medical history: The following factors are risk factors for MAS:

1. Pregnant mothers have pregnancy toxemia, pre-eclampsia, and diabetes;

2, pregnant mothers have obstetric complications, prolonged labor, amniotic fluid contaminated by meconium;

3, expired birth, full-term small sample; abnormal fetal heart, intrauterine distress; suffocation at birth and tracheal aspiration in the trachea.

(B) clinical manifestations: the clinical manifestations of children with MAS vary according to the severity of hypoxia damage and the amount and viscosity of meconium-stained amniotic fluid.

1. If the child is exposed to meconium-contaminated amniotic fluid for >4-6 hours in the uterus, the whole body skin, nails and umbilical cord are dyed yellow-green or dark green at birth.

2, respiratory distress: mainly manifested as shortness of breath (> 60 times / min), nasal fan, respiratory three concave signs and cyanosis. Due to the severity of meconium-contaminated amniotic fluid, the degree of respiratory distress can vary, and general cases often occur within 4 hours after birth. Mild people only show temporary dyspnea and often self-heal. Heavier people have difficulty breathing and bruising, but they need to inhale 40% oxygen to maintain normal PaO2 and PaCO2. Severe cases may die within a few minutes after birth or severe dyspnea and bruising within a few hours after birth. Generally, oxygen therapy is ineffective and requires comprehensive treatment such as mechanical ventilation. Some children may only show mild respiratory distress at the beginning, but after a few hours, the condition may worsen due to chemical pneumonia.

3, barrel chest: thick meconium-contaminated amniotic fluid inhalation, children may cause airway obstruction or semi-blocking. The clinical manifestations of acute airway obstruction are wheezing breathing, cyanosis, and must be immediately recruited by the trachea. In children with airway obstruction, due to gas retention, the anteroposterior diameter of the thorax increases with barrel chest, shallow breathing, decreased breathing sound or wet rales and wheezing. When a pneumothorax occurs, cyanosis and dyspnea may increase suddenly.

4, some children can be complicated by persistent pulmonary hypertension (see persistent pulmonary hypertension).

Simple amniocentesis is easier to absorb and there are fewer secondary pneumonia. Meconium amniotic fluid inhalers may have atelectasis, emphysema, mediastinal emphysema and pneumothorax with different degrees of obstruction. Severe oxyacidosis can cause intracranial hemorrhage and pulmonary hemorrhage. Patients with prolonged disease often have interstitial pneumonia and pulmonary fibrosis.

Differential diagnosis

Symptoms of meconium in amniotic fluid are confusing:

Amniotic fluid: normal amniotic fluid in full-term pregnancy is slightly opaque and opaque. It can be seen that there is a small piece in the amniotic fluid. If the amniotic fluid is mixed with blood, it is bloody amniotic fluid.

Amniotic fluid fecal dye: Amniotic fluid fecal dye refers to the relative hypoxia of the fetus in the uterus, causing the anus to relax, and the fetus is discharged into the amniotic fluid, causing amniotic fluid pollution.

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