As we all know, fetal stool is in the fetal intestine, but where does it come from when the fetus is in the mother’s belly and not eating? Fetal feces is 80% water, and the other 20% is fetal stool, which contains fetal hair, shed cells, amniotic fluid, intestinal secretions including pancreatic enzymes, bile acids and bile pigments, pH 7.10-7.20, which is conducive to the growth of bacteria. The external appearance is viscous, dark green, yellowish green or dark green, odorless and non-smelly. It is true that fetal stool does not stink. The fetus swallows amniotic fluid in the mother’s belly. Normal amniotic fluid is transparent and is essentially an outgrowth of the fetal extracellular fluid, and all the urine excreted by the fetus is also in the amniotic fluid, and fetal stool is not normally excreted in the amniotic fluid. Amniotic fluid has to protect the fetus, so that the fetus in the uterus to do the appropriate breathing movement, limb movement, conducive to development, prevention and control of joint fixation, fetal deformities and adhesions of fetal limbs; can maintain a constant temperature in the uterus, buffering external pressure; conducive to the balance of the amount of fetal fluids, the formation of the anterior amniotic fluid sac at the time of labor, expansion of the internal and external cervical opening and vagina. Babies soak in water before they are born, so newborns like to swim after birth. So what happens when the fetal stool runs into the amniotic fluid? That is due to the mother, the mother smoking, anemia, hypertension, diabetes, cardiovascular disease, etc. to make the placenta incompetent, or fetal umbilical cord abnormalities, umbilical cord around the neck, umbilical cord twisting, umbilical cord knotted so that the fetus acute or chronic hypoxia, intestinal wall spasm, anal dilatation relaxation, fetal stool elimination. Furthermore, during delivery, a variety of causes lead to obstruction of fetal blood flow, generating hypoxia and stimulating parasympathetic nerves causing fetal defecation contaminating the amniotic fluid. That is, without acute or chronic hypoxic factors in the uterus, fetal feces will not run into the amniotic fluid. Meconium contamination of the amniotic fluid is a prerequisite for fetal feces to run into the lungs. Amniotic fluid contaminated by meconium in the process of birth, due to asphyxia hypoxia and stimulation of the fetal whistling center, inducing fetal wheezing, whistling, so in the delivery of the fetus easy to meconium-contaminated amniotic fluid into the lungs, mild meconium aspiration pneumonia, severe meconium aspiration syndrome, pulmonary hypertension and increase the difficulty of treatment.