Causes of meconium-stained amniotic fluid

If there is fecal contamination in the amniotic fluid, it will often cause the amniotic fluid to be turbid, which is relatively harmful to the fetus and can easily cause respiratory distress in the fetus. If the fetus inhales such amniotic fluid, it can easily cause lung infection and other hazards after birth. There are many reasons for fecal contamination of amniotic fluid. If this happens, you must provide treatment and care. Let us understand the causes of fecal contamination of amniotic fluid.

Causes of meconium-stained amniotic fluid

1. Fetal maturation theory

It is believed that meconium staining of amniotic fluid is a physiological phenomenon. The fetus begins to swallow and have intestinal peristalsis at 16 to 18 weeks. The fetus swallows components such as vernix caseosa, vellus hair, and shed epidermal cells in the amniotic fluid, which are concentrated with bilirubin metabolites in the gastrointestinal tract to form meconium. The color of the meconium depends on the amount of bilirubin. As the gestational age increases, the fetal vagal nerve tone becomes stronger, gastrointestinal motility becomes more frequent, meconium becomes more abundant, and the rate of meconium staining of the amniotic fluid increases. Clinically, it has been found that the gestational age is positively correlated with the rate of meconium staining of the amniotic fluid. The rate of meconium-stained amniotic fluid is low in premature births and those with a gestational age of less than 38 weeks, and some cases of meconium-stained amniotic fluid have good obstetric and neonatal outcomes.

2. Fetal distress theory

The fetus is relatively hypoxic in the uterus, causing its anus to relax and meconium to be discharged into the amniotic fluid, causing amniotic fluid contamination. Elucidate the meconium staining of amniotic fluid from a pathological perspective. Meconium-stained amniotic fluid is the result of fetal ischemia and hypoxia. When the fetus is ischemic and hypoxic, the body redistributes blood flow in order to ensure blood supply to important organs such as the heart and brain. The blood supply to the digestive system is reduced, gastrointestinal motility increases, the anal sphincter relaxes, and meconium is excreted. Hypoxia can cause the release of fetal vasopressin, which promotes colon motility. There are also reports that as the degree and duration of hypoxia increase, more intestinal hormones appear in the upper digestive tract of the fetus. This peptide can promote intestinal

Treatment and care of meconium-stained amniotic fluid:

1. If the amniotic fluid is found to be meconium-stained before delivery: the pregnant woman should be advised to lie on her left side, count the fetal movements, and give oxygen. Strengthen fetal monitoring, including NST, B-mode ultrasound, and umbilical blood flow S/D examination to evaluate the fetus, placenta, amniotic fluid quality and quantity, and amniotic fluid distribution. The sensitivity of type B ultrasound in diagnosing meconium-stained amniotic fluid is low, at about 42%. Various obstetric comorbidities and complications should be actively dealt with, and pregnancy should be terminated promptly if there are indications for cesarean section. For those without obstetric abnormalities, there is no need for excessive intervention.

2. Meconium-stained amniotic fluid is found during the incubation period: If meconium-stained amniotic fluid is found after rupture of membranes, the first thing to consider is whether there is low fetal reserve, poor placental function, and possible factors causing fetal distress. Actively correct and treat pathogenic factors, assess the condition of the fetus, and decide on the mode of delivery based on the progress of labor. The following aspects can be considered. For patients with grade I meconium-stained amniotic fluid, close monitoring and continuous fetal heart rate monitoring are emphasized. If there are no other obstetric abnormalities, there is no need for excessive intervention, but all preparations should still be made to rescue neonatal asphyxia. Although there are differences in the treatment of grade II meconium-stained amniotic fluid, the treatment is generally the same as grade I. For patients with grade III meconium-stained amniotic fluid, most domestic and foreign reports believe that if accompanied by abnormal fetal heart rate monitoring or oligohydramnios, the morbidity and mortality rates of their neonates will increase significantly, so it is advisable to end the delivery as soon as possible by cesarean section.

3. Meconium-stained amniotic fluid is found during the active period: The amniotic fluid is clear at the beginning of labor, and meconium-stained amniotic fluid is found during the active period, indicating the presence of factors causing fetal ischemia and hypoxia. Common symptoms include long labor, cephalopelvic disproportion, abnormal fetal position, prolonged squeezing of the fetus by uterine contractions, acute ischemia and hypoxia leading to decompensation of the mechanism and meconium discharge. Vaginal delivery is the main option at this time, but monitoring should be strengthened, the labor process should be shortened, and assisted vaginal delivery can be performed to end the labor as soon as possible.

4. Treatment of newborns: Because meconium contains bacteria, pregnant women with this condition are in a high-risk pregnancy and the child is a high-risk baby. If the disease continues to develop, it will cause infection in the neonate, leading to dangerous diseases such as sepsis and pneumonia. The treatment of infants with meconium-stained amniotic fluid requires the joint efforts of obstetricians and pediatricians. Immediately after the fetus is delivered, the airway is cleared manually or with a suction tube, and endotracheal intubation and negative pressure suction are performed for those who are suffocating. However, positive pressure ventilation and respiratory stimulants can cause larger fecal matter to enter the lower respiratory tract. Patients with grade III meconium-stained amniotic fluid, low Apgar scores, acidosis, and asphyxia will be sent to the neonatal ward for treatment after rescue.