What is the cause of polyhydramnios? Radionuclide tracing proves that amniotic fluid is constantly exchanged between fetus and mother to maintain dynamic balance. Before keratinization, the fetus exchanges through swallowing, breathing, urination and skin and umbilical cord. When the amniotic fluid exchange is unbalanced, there is too much or too little amniotic fluid. The exact cause of polyhydramnios is not very clear, and it is more common in the following clinical situations.
1. Fetal malformation Among pregnant women with polyhydramnios, about 20% ~ 50% are complicated with fetal malformation, among which central nervous system and upper digestive tract malformation are the most common. In anencephaly, encephalocele and spina bifida fetus, meninges are exposed, choroidal tissue hyperplasia and exudate increase, resulting in polyhydramnios. In anencephaly and severe hydrocephalus, due to the loss of central swallowing function, no swallowing reflex, lack of antidiuretic hormone and increased urine volume, polyhydramnios are caused; Esophagus or small intestine atresia and pulmonary hypoplasia can not swallow and inhale amniotic fluid, which can all lead to polyhydramnios due to amniotic fluid accumulation.
2. Multiple pregnancy Multiple pregnancy complicated with polyhydramnios is 10 times that of single pregnancy, especially identical twins, which often occur in one of the heavier fetuses. Because of poor blood circulation between identical twins, the dominant fetus has more blood circulation and increased urine volume, resulting in polyhydramnios.
3. Various diseases of pregnant women and fetuses, such as diabetes, ABO or Rh blood group incompatibility, severe fetal edema, pregnancy-induced hypertension, acute hepatitis and severe anemia of pregnant women. The fetal blood sugar of pregnant women with diabetes will also increase, causing polyuria and discharging into amniotic fluid. When the blood type of mother and fetus is incompatible, the placenta is heavier. It has been reported that when the placental weight exceeds 800g, 40% is complicated with polyhydramnios, and chorioedema affects fluid exchange, which is the pathological basis.
4, placental umbilical cord lesions placental villous hemangioma, umbilical cord sail attachment can sometimes cause polyhydramnios.
5. Idiopathic polyhydramnios accounts for about 30%, and there are no abnormalities in pregnant women, fetuses or placentas, and the reasons are unknown.
Types of polyhydramnios Acute polyhydramnios: It mostly occurs in 20-28 weeks of pregnancy. Due to the rapid increase of amniotic fluid, the uterus grows rapidly within a few days, like a full-term pregnancy or a twin pregnancy uterus. In a short time, due to the rapid enlargement of the uterus and the uplift of the diaphragm, the expectant mother has difficulty breathing, can not lie flat, and even cyanosis appears. Expectant mothers will feel pain because of excessive abdominal tension, and constipation will also occur because of reduced food intake. Because the swollen uterus compresses the inferior vena cava, it will affect the venous return, causing edema and varicose veins of the lower limbs and vulva. Expectant mothers can only walk sideways.
Chronic polyhydramnios: It mostly occurs in 28-32 weeks of pregnancy, and amniotic fluid can gradually increase within a few weeks, which belongs to moderate slow growth. Most expectant mothers can adapt, and the height and abdominal circumference of uterus are often found to be larger than those of expectant mothers in the same period during prenatal examination. Expectant mothers with polyhydramnios will find that their abdominal wall skin is shiny and thin during physical examination, and feel great skin tension during palpation, with fluid tremor, unclear fetal position, distant fetal heart or inaudible. Expectant mothers with polyhydramnios are prone to pregnancy-induced hypertension, abnormal fetal position and premature delivery. Sudden contraction of uterus after rupture of membrane can cause placental abruption. When the membranes rupture, the umbilical cord can slide out with amniotic fluid, causing umbilical cord prolapse. The postpartum uterus is too large, which is easy to cause uterine inertia and lead to postpartum hemorrhage.
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