Patient's question:
Where are the hospitals in Nanchong that perform amniocentesis? How much does it cost, and what is the procedure like? Is there any danger or potential aftereffects? Please help me out, thank you.Doctor's answer:
Nanchong Women's Hospital offers amniocentesis, which is an invasive prenatal diagnostic procedure. Generally, we first take the mother's blood for screening. After screening, if the mother is reported to have a certain risk level, it indicates the likelihood of having a child with abnormalities. In newborns, without any screening or intervention, approximately 1 in 700 children may have this condition.Now, with screening, by examining the mother's blood-related baseline, we set a risk threshold. If the risk reaches 1 in 250, meaning the mother has a 1 in 250 chance of carrying a child with trisomy 21, we recommend amniocentesis. This involves directly collecting the fetal epidermal cells that have fallen into the amniotic fluid and then culturing them to examine their chromosomes to determine if there is an excess. This is how the condition is diagnosed.
Checking the fetus through the mother is safe and only requires a single blood draw from the mother. However, it only indicates the risk level—it cannot confirm whether the child has the disease. A definitive diagnosis must be made through amniocentesis. While it does carry risks, the overall risk rate leading to fetal miscarriage is generally no more than 1%.
In large or medium-sized hospitals, the principle is that amniocentesis must be performed under ultrasound guidance. This means we must monitor the procedure with ultrasound to avoid the fetus and the placenta, thereby minimizing the risk of injury to the child.
If you want to confirm whether the child has the disease, the risk is usually considered worth taking by doctors. Because if you don’t take the risk, the burden of having a child with intellectual disabilities—whether on society or the family—would be even heavier. Therefore, we still strongly recommend this procedure for high-risk populations. The risk is unnecessary.
Amniocentesis is a method of prenatal diagnosis and is generally suitable for mid-pregnancy. Amniotic fluid exists in the amniotic cavity. The amniotic cavity forms on the seventh day after fertilization, and amniotic fluid begins to accumulate. At 12 weeks of pregnancy, the volume of amniotic fluid is about 50 milliliters, at 20 weeks it is about 400 milliliters, and at 36–38 weeks it is about 1,000–1,500 milliliters, slightly decreasing near term.
The optimal time for amniocentesis to extract amniotic fluid for prenatal diagnosis is between 16 and 20 weeks of pregnancy. At this stage, the fetus is small, and there is relatively more amniotic fluid. The fetus floats in the fluid, surrounded by a wide band of amniotic fluid, making it less likely to be injured during needle insertion. Extracting 20 milliliters of amniotic fluid only accounts for 1/20 to 1/12 of the total volume, preventing sudden shrinkage of the uterus and miscarriage. Additionally, this period has the highest proportion of viable cells in the amniotic fluid, ensuring high cell culture survival rates. The cells can then be used for karyotyping, chromosomal genetic disease diagnosis, and gender determination. Amniotic fluid cells can also be used for DNA-based genetic disease diagnosis and metabolic disease diagnosis.
Measuring alpha-fetoprotein (AFP) in the amniotic fluid can diagnose open neural tube defects in the fetus. In the later stages of pregnancy, amniocentesis can determine blood type, bilirubin, lecithin, sphingomyelin, and placental lactogen to assess maternal-fetal blood type incompatibility, hemolysis, fetal lung maturity, skin maturity, and placental function.
The steps for amniocentesis are as follows. Pregnant women with indications first undergo ultrasound to determine the placental position and fetal condition, avoiding accidental injury to the placenta. If ultrasound is unavailable, a palpable, cystic area with a floating fetal body can be identified to avoid the placenta. After selecting the needle insertion point, the skin is disinfected, a sterile drape is placed, and local anesthesia is administered. A spinal needle with a stylet is inserted vertically at the chosen point. Two "loss of resistance" sensations are felt as the needle passes through the abdominal wall and uterine wall. The stylet is then removed. A 2-milliliter syringe is used to withdraw 2 milliliters of amniotic fluid, which is discarded, as this portion may contain maternal cells. A 20-milliliter syringe is then used to withdraw 20 milliliters of amniotic fluid, which is divided into two sterile test tubes and sealed. The needle is removed, covered with sterile gauze, and pressed for 2–3 minutes. The pregnant woman is then advised to rest for 2 hours.
The collected amniotic fluid is centrifuged for 5–10 minutes. The supernatant is used for biochemical tests, while the sediment is used for cell culture or DNA extraction.