What is Amniotic Fluid?

The fluid that fills the amniotic cavity is called amniotic fluid. The source, amount and composition of amniotic fluid varies with the gestational week. In early pregnancy, amniotic fluid is mainly dialysate from maternal serum that enters the amniotic cavity through the placenta, and a small amount leaks from the surface of the placenta and umbilical cord. When fetal blood circulation is formed, the fetal water and small molecules can seep through the skin of the fetus that has not been keratinized, forming part of the amniotic fluid. Fetal kidneys have been excreted from 11 to 14 weeks of pregnancy, so urine excreted by the fetus after the second trimester is an important source of amniotic fluid.

Basic Information

Chinese name

Amniotic fluid

Features

Protect fetus and reduce maternal damage

The function of amniotic fluid

Protect the fetus

A certain volume of amniotic fluid can provide a large range of activities for the fetus, enable the fetus to perform appropriate breathing exercises and physical activities in the uterine cavity, prevent joint fixation, limb deformity and fetal limb adhesion, which is beneficial to the development of the fetus.

2. Keep the intrauterine temperature constant

Amniotic fluid can keep the temperature in the uterine cavity constant, so that metabolic activities in the fetus can be performed under normal and stable conditions.

3. Conducive to fetal fluid balance

The fetus can rely on amniotic fluid to protect its fluid balance. When there is too much water in the fetus, it can be discharged into the amniotic fluid in the way of fetal urine; in addition to the controlled drainage, the amniotic fluid can be swallowed to compensate for dehydration.

4.Buffer external pressure

Amniotic fluid has the effect of balancing external pressure, which can obviously reduce the impact of external violence and protect the fetus. Moderate amniotic fluid can also prevent fetal hypoxia caused by direct compression of the uterine wall and fetus on the umbilical cord.

5. Role in labor

In labor, the uterus contracts and the intrauterine pressure increases. The amniotic fluid can conduct pressure on the cervix, form the anterior amniotic fluid sac before the fetal head is exposed, expand the cervix, outer mouth and vagina, and reduce the time spent by the direct compression of the body tissues Cervical and vaginal damage caused by a long time.

Amniotic fluid

Excessive amniotic fluid

The amount of amniotic fluid during pregnancy is more than 2000ml, which is called polyhydramnios. The incidence is 0.5% to 1%. The amount of amniotic fluid increases sharply within a few days and is called acute polyhydramnios; the amount of amniotic fluid slowly increases over a long period of time and is called chronic polyhydramnios.

Too much amniotic fluid can have adverse effects on both the mother and the fetus. As the uterus grows too large, the diaphragm moves upwards and compresses the chest, causing the mother to breathe fast, the heartbeat to accelerate, and indigestion. Increased abdominal pressure causes varicose veins in the lower limbs and edema in the lower limbs and vulva. It is easy to cause contraction fatigue and postpartum bleeding during childbirth. When there is too much amniotic fluid, the fetus is too floating in the uterus, which is prone to malposition. When the water is broken, umbilical cord prolapse is often seen.

2. Too little amniotic fluid

When the amount of amniotic fluid is less than 300ml, it is called oligohydramnios. Many congenital malformations, especially urinary system malformations, are associated with oligohydramnios, such as congenital kidney deficiency, renal dysplasia, polycystic kidney disease, and urethral stricture or atresia. In addition, placental dysfunction, expired pregnancy, placental aging, etc. can cause a decrease in amniotic fluid volume.

Pregnant women often feel pain due to fetal movements. The abdominal circumference and the height of the uterine floor are less than the month of pregnancy. Fetal movement is limited and natural turning is not easy. Pregnancy is prolonged, often more than 2 to 3 weeks beyond the expected date of delivery. In the process of childbirth, primary uterine contraction weakness or uncoordinated uterine contraction often occurs, the uterine opening expands slowly, and the prolonged first stage of labor is prone to occur. Amniotic fluid is rare, sticky, and mostly yellow-green, which can cause fetal hypoxia. Various developmental abnormalities caused by lack of amniotic fluid, such as oligohydramnios occurred in early pregnancy, part of the fetal surface may adhere to the amniotic membrane, or form an amniotic membrane band, causing fingers or limbs to be disconnected; if oligohydramnios occurs in late pregnancy, fetal skin Dry like parchment. Due to the lack of amniotic fluid, the fetus is in a mandatory position in the womb, which is susceptible to compression and causes special musculoskeletal deformities, such as hand and foot deformities, back flexion, torticollis, and upper and lower limb bending.

Amniotic fluid treatment

Excessive amniotic fluid

(1) Mild amniotic fluid requires no special treatment, and most of them can be adjusted automatically in a short time.

(2) Those with normal fetuses: Etiology treatment: Etiology should be searched for actively treating maternal diseases such as diabetes and hypertension during pregnancy. Maternal and child blood type incompatibility, if necessary, intrauterine blood transfusion treatment is feasible. Prostaglandin synthase inhibitor has anti-diuretic effect, can inhibit fetal urination and reduce the amount of amniotic fluid, but it should not be used for a long time. Immature fetal lungs should be prolonged as long as possible. Severe symptoms can be reduced by abdominal amniocentesis to relieve symptoms.

(3) Patients with fetal malformations: Terminate the pregnancy as soon as possible. The termination method depends on the amount of amniotic fluid and cervical maturity.

2. Too little amniotic fluid

(1) Patients with fetal malformations: termination of pregnancy as soon as possible after diagnosis.

(2) People with normal fetus

1) Expectation of treatment: If the fetal lung is immature, there is no obvious fetal malformation and the placenta is normal, it is feasible to expect treatment. During this period, the mother was ordered to count fetal movements, perform electronic fetal monitoring, and closely monitor the fetal condition. If conditions permit, amniotic cavity perfusion fluid method can also be used to reduce the incidence of fetal heart rate deceleration, amniotic fluid feces staining rate and cesarean section rate. At the same time, as the case may be, appropriate tocolytic inhibitors are used to prevent preterm birth.

2) Termination of pregnancy: Those who are pregnant at term and whose fetuses can survive outside the uterus should terminate pregnancy in time; Those who have severe placental dysfunction, fetal distress or low amniotic fluid and severely contaminated meconium during the rupture of the membrane, it is estimated that they cannot pass For vaginal delivery, cesarean section should be used to terminate pregnancy; fetal reserve is still good, and those with mature cervix can be induced by oxytocin after breaking the membrane under close supervision.