It is the sterile needle aspiration of fluid from the amniotic sac for analysis and gender test. This procedure is recommended when:
- The mother is older than age 35.
- The couple has already had a child with a chromosomal abnormality (such as Down syndrome) or a metabolic disorder (such as Hunter’s syndrome).
- The mother is a carrier of an X-linked genetic disorder, such as hemophilia, in which she has a 50% chance of passing the gene to a son.
- A parent is known to have a condition, such as Huntington’s chorea, that is passed on by autosomal dominant inheritance, giving the baby a 1 in 2 chance of inheriting the disease.
- Both parents are carrier of an autosomal recessive inherited disorder, such as Tay-Sachs disease or sickle-cell anemia, and thus have a 1 in 4 chance of bearing an affected child.
- Results of triple screening test and ultrasound are abnormal and amniocentesis test is necessary to determine whether there is a fetal abnormality.
Amniocentesis procedure is really important
The amniocentesis procedure is valuable because it can be used to:
- Detect fetal abnormalities, particularly chromosomal and neural tube defects;
- Detect hemolytic disease of the fetus;
- Diagnose metabolic disorder and amino acid disorders;
- Assess fetal lung maturity (the lungs are the last organs to ready to function on their own);
- Detect fetal age and maturity, especially fetal lung maturity;
- Measure amniotic levels of estriol and fetal thyroid hormone;
- Identify fetal gender;
- Amniotic liquid can be tested for a fetus’s Rhesus factor.
Aspiring toward aspirate
To begin, ask the mother to chance into an examination gown and empty her bladder. Then explain that she’ll position on the examining table on her back and her body will be draped so that only her abdomen is exposed. During the test, fetal heart rate (FHR), maternal vital signs, and ultrasound are monitored. The doctor:
- Prepares the skin with antiseptic and alcohol;
- Injects the skin with local anesthesia to numb the area;
- Inserts a 20G spinal needle with a stylet into the amniotic cavity;
- Aspirate amniotic fluid and places it in an amber or foil-covered test tube.
General risks of amniocentis
The risks of amniocentesis include spontaneous abortion, trauma to the fetus and placenta, bleeding, premature labor, infection, and Rh sensitization from fetal bleeding into the maternal circulation. Because of the potential amniocentesis risks, the severity of possible complications, it is contraindicated as a general screening test.
Finding meaning in amino findings
The abnormal amniocentesis results or failure of the tissue cultures to grow many necessitate repetition of the test.
Chorionic villi sampling
The cvs pregnancy test is performed between 8 and 10 weeks of gestation. The cvs test (also known as chorionic villi sampling) involves aspirating chorionic villi from the placenta for prenatal diagnosis of genetic disorders. The chorionic villus is a fingerlike projection that surrounds the embryonic membrane and eventually gives rise to the placenta. Cells obtained from the sample are of fetal – rather than maternal – origin and thus can be analyzed for fetal abnormalities. Expert believe that villi in the chorion frondosum reflect fetal chromosome, enzyme, and deoxyribonucleic acid (DNA) content.
Two sorts of samples
Either a transcervical or transabdominal approach can be used to obtain chorionic villus sampling as specimen. In transcervical sampling, a sterile catheter is introduced into the cervix using direct visualization with real-time ultrasonography. A small portion of chorionic villi sampling is aspirated through the catheter into a syringe. In transabdominal sampling, the maternal abdomen is cleaned and an 18G to 20G needle is inserted into the chorion frondosum under ultrasound guidance. The specimen is then aspirated into a syringe. Aspirated villi are placed into a sterile medium for cytogenic analysis.
Painting a picture of the fetus
The cells from the villi normally have the same genetic and biochemical makeup as the embryo. Therefore, examining villi cells provides a complete picture of the genetic make-up of the developing fetus. CVS can detect fetal diseases. The test also identifies the gender, allowing early detection of X-linked condition in male fetuses.
Test complications include failure to obtain tissue, ruptured membranes or leakage of amniotic fluid, bleeding, intrauterine infection, spontaneous abortion, contamination of the specimen, and possible Rh isoimmiunization. If the mother is Rh-negative, administering RhoGAM is indicated. This is to cover the risk of Rh sensitization from the procedure. Also, recent research indicates an indication of limb malformations in neonates whose mother have undergone CVS. However, this incidence appears to be low when CVS is performed after 10 weeks of gestation.
Many women feel phsycially and emotionally drained after undergoing this procedure. Advise the mother to have someone drive her home. Tell her not to make other plans for the rest of the day. Instruct her to call her health care provider with any concerns or symptoms of complications, such as fever, vaginal discharge, vaginal bleeding, or cramping.