Metabolites in amniotic fluid include creatinine, uric acid, urea, and the like. For example, creatinine in amniotic fluid is a metabolite of muscle creatine, which is discharged into the amniotic fluid through the urine of the fetus, so the creatinine value in the amniotic fluid is related to the maturity of the fetal kidney. In the second trimester of pregnancy, amniotic fluid creatinine>176.8μmol/L, which indicates the muscle weight of the fetus, and indicates that there are one million functional glomeruli, which is the fetal kidney maturity. In amniotic fluid creatinine, the fetus is mature but the birth weight is too low. When pregnant women suffer from kidney disease or pregnancy-induced hypertension syndrome (pregnancy-induced hypertension), amniotic fluid creatinine can be pseudo-increased, so serum creatinine should also be checked in pregnant women. Amniotic fluid specimens are usually obtained by amniocentesis by a general practitioner.

Basic Information

Specialist classification: maternity check check classification: biochemical examination

Applicable gender: whether women are fasting: not fasting

Analysis results:

Below normal:
In amniotic fluid creatinine, the fetus is mature but the birth weight is too low.

Normal value:
Early pregnancy: 70.7-97.2
Full-term pregnancy: 159.1-353.6

Above normal:
When pregnant women suffer from kidney disease or pregnancy-induced hypertension, amniotic fluid creatinine can be pseudo-increased, so serum creatinine should also be checked.

negative:

Positive:

Tips: If the amniotic fluid specimen is not tested on the day, it can be stored in the refrigerator for 3 days. Normal value

Early pregnancy 70.7 ~ 97.2μmol / L (0.8 ~ 1.1mg / dl).

Full-term pregnancy 159.1 ~ 353.6μmol / L (1.8 ~ 4.0mg / dl).

Clinical significance

1, amniotic fluid creatinine range is wide, is 159.1-353.6μmol / L, generally higher than the plasma value. The creatinine concentration greater than or equal to 176.8 μmol/L suggested fetal maturation, 132.6-175.9 μmol/L was suspicious, and 131.7 μmol/L was immature.

2, amniotic fluid creatinine in the late pregnancy> 176.8μmol / L, which represents the muscle weight of the fetus, and indicates that there are one million functional glomeruli, which is the fetal kidney maturity. In amniotic fluid creatinine, the fetus is mature but the birth weight is too low. When pregnant women suffer from kidney disease or pregnancy-induced hypertension syndrome (pregnancy-induced hypertension), amniotic fluid creatinine can be pseudo-increased, so serum creatinine should also be checked in pregnant women.

3, creatinine in amniotic fluid comes from fetal urine, which is a fetal metabolite, and its excretion reflects the maturity of glomeruli. Although creatinine is a reliable chemical indicator in terms of fetal maturity, its concentration is interfered by several factors. Therefore, attention should be paid to the solution of anaesthetic and maternal maturity. 1 The creatinine concentration in amniotic fluid is affected by amniotic fluid volume and fetal muscle development. Degree and impact; 2 pregnant women plasma creatinine concentration will affect amniotic fluid creatinine concentration.

High results may be diseases: Precautions for pregnancy-induced hypertension syndrome

1. When measuring creatinine, the temperature of each tube should be reduced to room temperature, and then colorimetric, because the temperature increase can make the color of bitter acid solution deeper, but the standard and measurement are not consistent.

2. In order to ensure accurate and reliable test results, each test should include quality control serum, and the measured quality control value should fall within the allowable range.

3, WHO recommended creatinine picric acid colorimetric method OCV is ± 0.4%, RCV is ± 8%, China's recommended RCV is 8%.

4, such as homemade quality control serum, should pay special attention to the infection of hepatitis virus, and do a good job of disinfection.

5. If the sample sample is not tested on the day, it can be stored in the refrigerator for 3 days. If it is not tested for a long time, it can be stored at -20 °C.

6, slight hemolysis can make creatinine determination results are high, severe hemolysis can interfere with the results.

7. The protein-free blood filtrate used for the determination of creatinine is affected by the pH value. When the pH value is below 2, the recovery rate can reach 100%.

8. Picric acid is toxic. Do not swallow or touch the skin. If it is inadvertently contacted, rinse it with plenty of water in time.

9, the quality of picric acid should be high: to use AR above the level of reagents, such as picric acid reagent is not pure, can increase the absorbance of the blank tube and affect the measurement results.

10. Colorimetric should be completed within 15 minutes after color development. If the time is too long, the non-specific reaction of picric acid with other substances in the blood filtrate will affect the accuracy of the determination results.

11. Bitter acid is an explosive. To prevent accidents, it is best to use plastic bottles and add a little distilled water.

Inspection process

Detection operation:

1. Take a test tube of 16mm×110mm, add 0.5ml of amniotic fluid, then add 4.5ml of 35mmol/L tungstic acid solution, and mix well. Centrifuge at 3000r/min for 10min, and take the supernatant for use.

2. Take another three test tubes, respectively indicating the measuring tube "U", the standard tube "S", and the blank tube "B".

3. Add protein-free blood filtrate to the measuring tube, add 3.0 ml of creatinine standard application solution to the standard tube, add 3.0 ml of distilled water to the blank tube, then add 1.04 mol/L picric acid reagent 1.0 ml to each tube, and add 0.75 mol/L hydrogen. 1.0 ml of sodium oxide solution.

4. Mix the mixture upside down and place it for 15 minutes. At a wavelength of 510 nm, use a spectrophotometer and adjust the “0” with a blank tube to read the absorbance of the measuring tube and the standard tube.

Not suitable for the crowd

1, amniocentesis should not be performed in the early stage of pregnancy.

2, pregnant women should not detect when they have a cold.

3, amniocentesis needs to obtain the consent of the pregnant woman and their families, and it is not appropriate to check for appropriate symptoms.

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.