The bilirubin in amniotic fluid is produced by the destruction of fetal red blood cells. The route to enter amniotic fluid may be through the lungs or skin, mostly unconjugated bilirubin, and high levels of bilirubin in amniotic fluid during early pregnancy. As the liver function of the fetus gradually matures and improves, the bound bilirubin in the fetus gradually increases, and the unconjugated bilirubin in the amniotic fluid gradually decreases. At the late pregnancy and the end stage, the concentration is extremely low, even 0. Since the content is too small, it is difficult to detect by general chemical methods, and the difference in absorbance is required to be measured. Amniocentesis can reflect the growth of the fetus in the uterus, maturity, and help identify the diagnosis of fetal hemolytic disease.

Basic Information

Specialist classification: maternity check check classification: biochemical examination

Applicable gender: whether women are fasting: not fasting

Tips: Amniocentesis is usually performed in the second trimester (16-21 weeks of gestation). Normal value

Early pregnancy <1.28 μmol/L (<0.075 mg/dl).

Full-term pregnancy > 0.43 μmol / L (> 0.025 mg / dl).

Clinical significance

In the case of hemolytic disease, this can be used as an indicator to determine whether to continue observation, intrauterine blood transfusion, induction of labor. Continued to rise in the second trimester, indicating that the fetus has intrauterine hemolysis. Amniotic fluid bilirubin pseudo-increased when pregnant women have elevated blood bilirubin (hepatitis, hemolytic anemia, cholestasis) or taking certain drugs (phenothiazine).

High results may be diseases: Rh blood group incompatibility, maternal and child blood group incompatibility considerations

Amniocentesis is usually performed in the second trimester (16-21 weeks of gestation). The urine should be drained before surgery, with both hands on the hips and gently turn the waist and abdomen. Then supine, use B-ultrasound to detect the positioning, select the puncture point, and puncture under strict aseptic operation conditions. Generally, about 20 ml of amniotic fluid is taken and placed in a clean and sterilized centrifuge tube for immediate inspection.

Inspection process

The detection operation is as follows:

After fully mixing, the wavelength is 600nm, the control tube is zeroed, and the absorbance of each tube is read; or the water is zeroed, the absorbance of the measuring tube and the control tube is read, and the difference between the absorbance of the measuring tube and the absorbance of the control tube (Au-Ac) is used. The corresponding bilirubin concentration was determined on the standard curve.

Not suitable for the crowd

1, amniocentesis is generally performed in the second trimester (pregnancy 16-21 weeks), early pregnancy, late are not suitable.

2, amniocentesis is aseptic operation, there is a risk of complications, the consent of pregnant women and their families should be obtained, and those without amniocentesis should not be carried out.

Adverse reactions and risks

1, maternal injury: puncture needle stab wound blood vessels caused by abdominal wall hematoma uterine subserosal hematoma. Occasionally, amniotic fluid enters the maternal blood circulation from the puncture hole and causes amniotic fluid embolism. The bladder was not emptied before the puncture, and the bladder was injured.

2, damage to the fetus, placenta and umbilical cord: puncture needle damage to the fetus can occur bleeding, stab wounds and umbilical cord can also occur bleeding or hematoma. Therefore, the source of bleeding should be identified when taking hemorrhagic amniotic fluid. If you suspect that you are from a fetus, you should continue to listen to the fetal heart.

3, amniotic fluid leakage: postoperative amniotic fluid leakage from the needle hole, resulting in too little amniotic fluid, affecting fetal development, and even cause miscarriage or premature birth.

4, abortion or premature delivery: the incidence of abortion or premature birth 0.1% -0.2%, often occurred within one week after surgery, even after the puncture, premature rupture of membranes leading to premature delivery.

5, intrauterine infection: postpartum may have maternal fever. Intrauterine infection can cause abnormal fetal development, or even fetal death. Therefore, amniocentesis should be strictly aseptic.