Patient's question:
Left and right, but I suddenly want to know the baby's blood type. If I need to know, do I have to go to the hospital to check this and that? Will this test be harmful to the baby? Is there a simpler method?Doctor's answer:
Amniocentesis is a method of prenatal diagnosis. It is generally suitable for prenatal diagnosis during the second trimester of pregnancy. Amniotic fluid exists within the amniotic sac; the amniotic sac forms from the fertilized egg on the seventh day of fertilization, and the production of amniotic fluid begins. At 12 weeks of pregnancy, the volume of amniotic fluid is 50 milliliters, at 20 weeks it is 400 milliliters, and at 36–38 weeks it is 1,000–1,500 milliliters. The volume of amniotic fluid slightly decreases as the due date approaches. The optimal time for amniocentesis to extract amniotic fluid for prenatal diagnosis is between 16 and 20 weeks of pregnancy. This is because the fetus is smaller at this stage, and there is relatively more amniotic fluid. The fetus floats in the amniotic fluid, surrounded by a wider band of amniotic fluid. When extracting amniotic fluid with a needle, it is less likely to injure the fetus. Extracting 20 milliliters of amniotic fluid only accounts for 1/20 to 1/12 of the total volume, which will not cause the uterus to suddenly shrink and lead to miscarriage. Moreover, during this period, the proportion of viable cells in the amniotic fluid is the highest, and the cell culture survival rate is high. This allows for the preparation of slides, staining, and fetal chromosome karyotype analysis, as well as the diagnosis of chromosomal genetic diseases and gender determination. Amniotic fluid cells can also be used to diagnose genetic diseases and metabolic diseases based on DNA. Measuring alpha-fetoprotein in the amniotic fluid can also diagnose fetal open neural tube defects. In the late stages of pregnancy, amniocentesis can measure blood type, bilirubin, lecithin, sphingomyelin, and placental lactogen to assess whether there is maternal-fetal blood type incompatibility, hemolysis, fetal lung maturity, skin maturity, and placental function.Because this procedure carries certain risks, the larger the baby, the more active it is, the greater the risk during the surgery. Although the puncture is performed under ultrasound guidance, if the placenta is on the anterior wall, there are limited areas to perform the puncture. You need to consider this carefully. However, if this is the reason, you must think carefully!