Also found in: Dictionary, Thesaurus, Acronyms, Encyclopedia, Wikipedia.
- vaginal bleeding. The appearance of blood could signal a problem.
- premature labor. Unusual abdominal pain and/or cramping may indicate the onset of premature labor. Mild cramping for the first day or two following the procedure is normal.
- signs of infection. Leaking of amniotic fluid or unusual vaginal discharge, and fever could signal the onset of infection.
- maternal/fetal hemorrhaging. While spotting in pregnancy is fairly common, bleeding following amnio should always be investigated.
- infection. Infection, although rare, can occur after amniocentesis. An unchecked infection can lead to severe complications.
- fetal injury. A very slight risk of injury to the fetus resulting from contact with the amnio needle does exist.
- miscarriage. The rate of miscarriage occurring during standard, second trimester amnio appears to be approximately 0.5%. This compares to a miscarriage rate of 1% for CVS. Many fetuses with severe genetic defects miscarry naturally during the first trimester.
- the trauma of difficult family-planning decisions. The threat posed to parental and family mental health from the trauma accompanying an abnormal test result can not be underestimated.
A common indication for amniocentesis is the suspected presence of erythroblastosis fetalis, which results from incompatibility of Rh factors in the fetal and maternal blood. Samples of amniotic fluid are analyzed for concentrations of protein and bilirubin. The higher the concentration, the stronger the evidence that erythrocytes are being destroyed, and measures must be taken to forestall the effects of the disorder on the fetus.
Another biochemical study involves measuring the level of alpha-fetoprotein (AFP) in the amniotic fluid. Abnormally high levels indicate an open defect of the spine, e.g., spina bifida or anencephaly.
Because of the ability to determine fetal maturation by amniotic fluid studies, it is possible to predict whether an infant will suffer from hyaline membrane disease at birth. A favorable ratio of lecithin to sphingomyelin indicates sufficient lung maturity.
When being performed for prenatal diagnosis, amniocentesis is usually offered to women 35 years or older, women with a child with a chromosomal abnormality, parents with a child with neural tube defect, and women with elevated serum alpha-fetoprotein, or when one parent has a chromosomal abnormality or is a carrier for a metabolic disease. Parents who agree to amniocentesis must be prepared to make a decision whether or not to abort the fetus if the laboratory tests indicate the presence of a birth defect. Frequently, however, parents who have a high risk for having an abnormal child find that the developing fetus is normal and the prognosis for delivery of a healthy baby is excellent.
During the procedure, the physician inserts a long pudendal needle into the mother's abdomen and into the amniotic cavity, avoiding the fetus and the placenta (which is located via ultrasonography). Local anesthesia is used to minimize discomfort. The patient is cautioned not to move during the procedure lest the needle become displaced. A syringe is attached and fluid is withdrawn. It is sometimes necessary to repeat the procedure because of an insufficient sample or unsuccessful laboratory testing. The repeat procedure is done several days after the first.
Following amniocentesis the patient is observed for changes in blood pressure, excessive leakage of fluid, and signs of infection. Hemorrhage from the placenta must be considered a possibility if the blood pressure begins to drop. Increased fetal activity or other signs of fetal distress such as changes in the fetal heart rate must be reported to the physician at once as they may warrant immediate measures such as delivery of the infant if it is considered to be viable. The Centers for Disease Control and Prevention publish a useful patient education booklet on amniocentesis titled “Amniocentesis for Prenatal Chromosomal Diagnosis,” which can be obtained by request from the CDC: Chronic Disease Division, Bureau of Epidemiology, Atlanta, GA 30333.
amniocentesisA procedure in which fluid is obtained by an ultrasonographically guided needle from the amniotic cavity—usually between weeks 15–17 of pregnancy—to detect foetal abnormalities by karyotyping or chemical analysis; accuracy is reported to be 99.4%; complication rate < 0.5% above the background pregnancy loss of 2–3%; foetal loss minimal.
Defects identified by amniocentesis
Cultured amniotic cells can be used for cytogenetic studies, DNA analysis (karyotyping) and enzyme assays; amniocentesis may not be necessary in women with increased AFP and a normal foetus by ultrasonography.
• Maternal age > 35;
• 3+ spontaneous abortions;
• Previous child with chromosome defect, metabolic disease, neural tube defect;
• Parent with or family history of chromosome defect(s);
• Possible carrier of X-linked disease.
amniocentesisObstetrics A procedure in which fluid is obtained by an ultrasonographically-guided needle from the amniotic cavity–usually between wks 15-17 of pregnancy to detect fetal abnormalities by karyotyping or chemical analysis; accuracy is reported to be 99.4%; complication rate < 0.5% above the background pregnancy loss of 2-3%; fetal loss minimal Defects identified by amniocentesis Cultured amniotic cells can be used for cytogenetic studies, DNA analysis–karyotyping, and enzyme assays. Cf Chorionic villus biopsy.
Amniocentesis—indications forMaternal age > 35 3+ spontaneous abortions Previous child with chromosome defect, metabolic disease, neural tube defect Parent, or family Hx of chromosome defect(s) Possible carrier of X-linked disease.
amniocentesis(am?ne-o-sen-te'sis) [ amnion + -centesis]
This procedure is usually performed no earlier than at 14 weeks' gestation. It is important that the analysis be done by experts in chemistry, cytogenetics, and cell culture. Cell cultures may require 30 days, and, if the test has to be repeated, the time required may be insufficient to allow corrective action. See: illustration
CAUTION!The procedure can cause abortion or trauma to the fetus.
The patient's knowledge about the procedure is evaluated, misconceptions corrected, and information provided as necessary. The patient is informed about sensations that she may experience and signs a consent form. The amniocentesis equipment is assembled; amber-colored test tubes are used (or clear test tubes covered with aluminum foil) to shield the fluid from light, which could break down bilirubin. Baseline vital signs and fetal heart rate are obtained, and the fundus is palpated for fetal position and fetal and uterine activity for 30 min before, during, and 30 min after the procedure. The patient is assessed for light-headedness, nausea, and diaphoresis as well as for anxiety, pain, and labor onset. During the procedure, emotional support is provided. After the procedure, the patient is positioned on her left side and is instructed to report unusual fetal hyperactivity or hypoactivity, clear or bloody vaginal drainage, uterine contractions, abdominal pain, or fever and chills, any of which is indicative of complications. Rh-negative women with an Rh-positive fetus should be given RhoGam. See: chorionic villus sampling
amniocentesisA method of obtaining early information about the health and genetic constitution of the growing fetus, by taking a sample of the fluid from the womb (AMNIOTIC FLUID) for analysis usually between the 15th and 18th week of pregnancy. Cellular debris in the fluid provides DNA for chromosome analysis and sex determination and the fluid contains specific substances characteristic of various diseases. The risk of fetal loss from this procedure is estimated to be 0.5% to 1% above the natural level of spontaneous abortion.
amniocentesisa technique for the diagnosis of congenital abnormalities before birth. In this procedure a sample of 10–15 cm3 of amniotic fluid surrounding the foetus is extracted through the abdominal wall using a surgical syringe, usually at about the 16th week of pregnancy. The sloughed-off embryonic cells contained in the fluid can be cultured to enable KARYOTYPE analysis, which shows the number and condition of the chromosomes. The fluid can also be analysed for the presence of chemicals which indicate biochemical and other defects (e.g. spina bifida).
Patient discussion about amniocentesis
Q. Can I get a little more information on amniocentesis…. hi all…..I am 38 years pregnant. I am expecting my 3rd child and I will have my amniocentesis test next week ………can I get a little more information on amniocentesis…. what else I can find and why do they take this and can it harm….. Please.
Q. what does enlarged heart mean? is it linked to down syndrome? My wife is 16 weeks pregnant. we did a prenatal US and we were told that the baby hes an enlarged heart and that we are advised to do amniocentesis. A friend of mine had a baby with down syndrome, and he was toled that if they have done this procedure, the doctors could have find it on time and abort the pregnancy. Is there a clear connection between the enlarged hart and the fact that the doctor advised us to do this procedure to down syndrome?
The protocol that most obstetrics use is that if there is anything abnormal in the US there is an automatic referral to an amniocentesis procedure.
the US has a lot of false alarms, so they must check with the more accurate procedure.