Polyhydramnios

Introduction to polyhydramnios Amniotic fluid volume has increased from the early pregnancy to the beginning of the last 4 weeks. The amount of amniotic fluid in a full-term pregnancy is about 1000 to 1500 ml. In any period of pregnancy, if the amount of amniotic fluid exceeds 2000 ml, it is called too much amniotic fluid. The increase in amniotic fluid rate is called chronic amniotic fluid. In the short term, the amniotic fluid increases sharply. It is called acute amniotic fluid. The excess amniotic fluid is more common in fetal malformation, twins, diabetes, and blood type incompatibility. When the amniotic fluid is too much, the appearance, traits and normality of amniotic fluid are not abnormal. basic knowledge The proportion of sickness: 0.0045% Susceptible population: pregnant women Mode of infection: non-infectious Complications: premature delivery, placental abruption

Causes of polyhydramnios

The radionuclide tracer test proves that amniotic fluid exchanges between the fetus and the mother to maintain dynamic balance. The fetus exchanges the skin, umbilical cord, etc. before swallowing, breathing, urinating and keratinization. When the amniotic fluid exchange is out of balance, it appears. The exact cause of polyhydramnios is too clear or too much, and it is clinically seen in the following situations.

Fetal malformation (35%):

Is the main cause of polyhydramnios, especially congenital nervous system malformations and digestive tract abnormalities, 18% to 40% of polyhydramnios with fetal malformations, amniotic fluid with the following high-risk factors, the incidence of fetal malformations Significantly elevated:

1. Fetal growth retardation;

2, premature delivery, amniotic fluid associated with spontaneous premature birth of fetal malformation rate of 24%, significantly higher than full-term delivery (incidence rate of 11%);

3, early onset, excessive amniotic fluid often occurs before the 32 weeks of pregnancy;

4. Cannot be explained by other high-risk factors.

(1) nervous system malformation: the most common, such as no brain, meningocele, etc., accounting for about 50% of the amniotic fluid deformity, because the meninges are exposed in the amniotic cavity, a large amount of body fluids seep through the cerebrospinal fluid, resulting in Excessive amniotic fluid; secondly, the brain and spinal cord are directly stimulated by amniotic fluid to cause an increase in urination; again, the lack of vasopressin in the posterior pituitary gland is also a factor that causes polyhydramnios.

(2) Digestive and respiratory malformations: mainly digestive tract atresia, such as esophageal atresia, duodenal atresia or stenosis.

(3) Abdominal malformation: During fetal development, the development of fetal abdominal cavity is incomplete due to various factors.

(4) hereditary pseudohypoaldosteronism (PHA): This is a congenital hyponatremia syndrome.

(5) Multiple malformations: In addition to the above-mentioned fetal malformations, congenital cerebral vascular malformations, cardiovascular malformations, pulmonary cystic adenomas, etc. are associated with polyhydramnios, multiple systems, multiple organ malformations often accompanied by polyhydramnios The mechanism is complex and the mechanisms of many diseases are not yet clear.

Multiple pregnancy (15%):

10% of twin pregnancies combined with polyhydramnios, the incidence of single-oval twins is four times higher than that of double-oval twins. In single-oval twins, the incidence of single-oval monochorionic twins is the highest. In particular, twin-transfusion syndrome, the rate of vascular anastomosis between single-oval and single-chorionic twin placenta is as high as 85% to 100%. The most common methods of vascular anastomosis are arterial-arterial, arterial-venous, and venous-venous anastomosis. The way is arterial-venous anastomosis.

Various diseases of pregnant women and fetuses (10%):

Such as diabetes, ABO or Rh blood group incompatibility, severe fetal edema, pregnancy-induced hypertension, acute hepatitis, severe anemia in pregnant women, fetal blood sugar in pregnant women with diabetes will also increase, causing polyuria and discharged into the amniotic fluid, when the mother and child blood type is incompatible, the placenta is more Heavy, it has been reported that when the placenta weight exceeds 800g, 40% of the amniotic fluid is combined, and the edema of the villus affects the fluid exchange.

Fetal accessory disease (5%):

The hormone secreted by the placenta may have a regulatory effect on amniotic fluid volume, especially human placental lactogen (HPL), which increases the concentration of HPL in placenta enlargement. On the other hand, placental villus lobules have HPL receptors, and idiopathic amniotic fluid. The HPL receptor is significantly reduced.

Placental villus hemangioma is a common benign tumor of the placenta, but it is rare in patients with a diameter of 5 cm or more. Placental villus hemangioma is often accompanied by excessive amniotic fluid.

Idiopathic polyhydramnios (30%)

About 30%, not including any pregnant women, fetal or placenta abnormalities, the cause is unknown.

Pathogenesis

1, due to digestive tract atresia or stenosis, the fetus can not swallow amniotic fluid, or slow absorption after swallowing, and the fetal urine volume is still the same, resulting in too much amniotic fluid, fetal respiratory tract is also one of the pathways of amniotic fluid metabolism, respiratory malformations can also lead to excessive amniotic fluid But very rare.

2, abdominal wall defects can cause umbilical bulging, visceral eversion, so that there is only a thin peritoneum between the abdominal cavity and the amniotic cavity, leading to extravasation of fetal fluid, and the occurrence of polyhydramnios, diaphragmatic defects are called sputum, the contents of the abdominal cavity Through the pupil into the chest cavity, the development of the fetal lung and esophagus is blocked, and the amniotic fluid swallowed and inhaled by the fetus is reduced, resulting in excessive amniotic fluid.

3, the fetal sensitivity to aldosterone is reduced, leading to hyponatremia, hyperkalemia, dehydration, increased fetal urine, fetal growth retardation and other symptoms, often accompanied by excessive amniotic fluid.

4. Due to the pressure difference between the two ends of the anastomosis, the blood can be transported from one fetus (the donor) to the other fetus (the recipient). The blood volume of the fetus is too much and polyuria, resulting in excessive amniotic fluid; The blood supply to the fetus is oliguria, resulting in too little amniotic fluid.

5, pregnant women with diabetes increased blood glucose levels, because blood sugar can pass through the placenta, fetal blood glucose concentration at the same time, causing fetal urine output increased, which may be the cause of excessive amniotic fluid caused by diabetes.

6. The pathogenesis of idiopathic amniotic fluid is not fully understood. There are still many polyhydramnios that cannot be explained by the above factors, and the incidence varies greatly. Panting et al reported that idiopathic amniotic fluid has a prognosis for perinatal infants. No significant effect, only the increase in cesarean section rate.

Amniotic fluid prevention

1, pay attention to rest, low-salt diet.

2, can take diuretic dihydro fluzamide 25mg, 3 times a day orally, or spleen and water, Wenyang gas.

3. The placenta after 20 weeks of gestation or normal position during childbirth is partially or completely detached from the uterine wall before delivery of the fetus, which is called placental abruption. Placental abruption is a serious complication in the third trimester of pregnancy. It has the characteristics of rapid onset and rapid development. If it is not treated in time, it can endanger the mother and child. The incidence of placental abruption: 1% to 2% abroad, domestic 0.46% to 2.1%. Care should be taken to prevent placental abruption and postpartum hemorrhage.

Amniotic fluid complications Complications premature placental abruption

Acute amniotic fluid patients with high abdominal pressure, venous return obstruction, genital and lower extremity edema, varicose veins, excessive uterine tension, prone to premature birth, when the membrane rupture, a large amount of amniotic fluid quickly flow, the uterus suddenly shrinks, easily causing placenta Early peeling.

Symptoms of polyhydramnios common symptoms amniotic fluid echo increased increased dyspnea fatigue fatigue pregnancy high fetal position abnormal constipation placental abruption postpartum hemorrhage varicose veins purpura

Excessive amniotic fluid causes abnormal uterine enlargement, increased pressure in the uterine cavity, and increased uterine tension. At the same time, increased uterine compression of adjacent organs is the main clinical manifestation of polyhydramnios. Symptoms usually occur when the amount of amniotic fluid exceeds 3000 ml.

1, acute amniotic fluid: more than 20 to 28 weeks of pregnancy, due to the rapid increase in amniotic fluid, the uterus rapidly increased within a few days, like the size of the full-term pregnancy or twin pregnancy, in a short period of time due to the extreme increase of the uterus, Yokohama Lifting up, breathing difficulties, not lying, even cyanosis, pregnant women with painful expression, excessive abdominal tension, pain and loss of food, constipation, due to the swelling of the uterus to compress the inferior vena cava, affecting venous return, causing lower extremities and genitals Puffiness and varicose veins, pregnant women are inconvenient to walk and can only lie on their side.

2, chronic polyhydramnios: about 98% and more occur in the 28 to 32 weeks of pregnancy, amniotic fluid can gradually increase in a few weeks, is a moderate increase in slow growth, most pregnant women can adapt, often in the prenatal examination, find the palace High, abdominal circumference is greater than the same period of pregnant women, more pregnant women in amniotic fluid physical examination, see abdominal bulging greater than the pregnancy month, the pregnancy chart shows that the palace height curve is beyond the normal hundred-digit number, the abdominal wall skin is bright, thin, feel the skin when palpation The tension is large, there is fluid tremor, the fetal position is unclear, sometimes the fetus and the fetus have a sense of floating, the fetal heart is far away or inaudible, the pregnant women with polyhydramnios are prone to complicated pregnancy-induced hypertension, abnormal fetal position, premature delivery, and the uterus after the membrane breaks. Downsizing can cause placental abruption. When the membrane is broken, the umbilical cord can slide out with the amniotic fluid to cause umbilical cord prolapse. The postpartum factor palace is too large to cause uterine contraction and lead to postpartum hemorrhage.

Excessive amniotic fluid examination

1. B-mode ultrasonography : The method of measuring the amount of amniotic fluid (AFD) in the vertical depth of a single largest amniotic fluid dark area shows that the distance between the fetus and the uterine wall is increased. If it exceeds 7 cm, it can be considered as excessive amniotic fluid (some scholars believe that it is more than 8 cm). Can diagnose too much amniotic fluid). If the amniotic fluid index method (AFI) is used, that is, the head height of the pregnant woman is 30°, the umbilical cord and the abdominal white line are used as the marker points, and the abdomen is divided into four parts to determine the maximum amniotic fluid dark areas of each quadrant. The domestic data is >18cm. Too much amniotic fluid. Phelan thinks that >20cm can be diagnosed. The AFI was significantly better than the AFD method. When the amniotic fluid is too much, the fetus only occupies a small part in the uterine cavity, and the limbs are in a free state, floating in the amniotic fluid, and can also find fetal malformations and twins at the same time.

2, amniocentesis and fetal angiography : in order to understand the fetal gastrointestinal malformation, first 76% diatrizoate 20 ~ 40ml into the amniotic cavity, after 3 hours, the contrast agent in amniotic fluid is reduced, the fetal intestine A contrast agent appears. Then 40% iodized oil 20 ~ 40ml (depending on the amount of amniotic fluid) into the amniotic cavity, turned left and right several times, because the fat-soluble contrast agent and fetal fat have a high affinity, half an hour, 1 hour after the injection, The film is taken separately for 24 hours, and the body surface of the fetus including the head, the trunk, the extremities and the external genitalia can be developed. Amniocentesis may cause premature delivery and intrauterine infection, and contrast agents and radiation may cause damage to the fetus and should be used with caution.

3, the detection of neural tube defects in the fetus: this type of fetal malformation is easy to merge with polyhydramnios. In addition to B-mode ultrasound, there are several detection methods:

1 Determination of amniotic fluid and maternal blood alpha-fetoprotein (-FP): in the fetus with open neural tube defect, -FP infiltrates into the amniotic cavity with cerebrospinal fluid. When pregnancy is combined with neural tube defect, the amniotic fluid -FP value is higher than normal. The pregnancy average is more than 3 standard deviations. The maternal serum -FP value exceeded the standard deviation of the normal pregnancy by more than 2 standard deviations.

2 maternal estrogen / creatinine (E / C) ratio determination: when combined with a neural tube defect fetus, the E / C ratio is lower than the mean of the normal pregnancy compared to the same period of more than 1 standard deviation.

3 amniotic fluid fast adherent cells, amniotic fluid acetylcholinesterase gel disk electrophoresis, amniotic fluid A and anti--FP monoclonal antibody position sandwich solid phase immunoradiation, can detect neural tube defects, several methods simultaneously Detection can make up for the deficiency of B-ultrasound and -FP method.

Diagnosis and identification of polyhydramnios

diagnosis

Can be diagnosed based on clinical performance and laboratory tests.

Differential diagnosis

1. Twin pregnancy: The uterus is larger than the pregnancy month, similar to the amniotic fluid uterus, but the twin fetal pregnancy is more frequent, the abdomen can touch more limbs and two fetal heads; two fetal heart sounds can be heard, B-mode ultrasound The check can be identified.

2, huge fetus: the low height of the uterus exceeds the gestational week of the same period, should be differentiated from polyhydramnios. The huge fetus does not have much amniotic fluid in the uterus. The fetus is large and the fetal heart is clear. B-mode ultrasound can help diagnose.

3, hydatidiform mole: similar to the amniotic fluid is too much for the uterus to grow rapidly, but the hydatidiform mole often has continuous vaginal bleeding, the uterus is soft, can not touch the carcass and can not hear the fetal heart sound, the ovary can increase the appearance of flavin Cysts, B-mode ultrasound and urinary chorionic gonadotropin determination can be identified.

4, pregnancy combined with large ovarian cysts: similar to the amniotic fluid, the abdominal enlargement is obvious, but the abdominal examination of the pregnant uterus is on one side, the size of the uterus is consistent with the pregnancy month or small, the fetal position and fetal heart is clear, B-mode ultrasound The echo of the uterine wall can be seen between the ovarian cyst and the amniotic cavity. The echo-free area around the fetus is normal. The fetus is active in the echogenic region of the amniotic cavity. It does not enter the cyst-free echo zone, and is easily identified with too much amniotic fluid.

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