Amniocentesis

Embryology - 16 Apr 2024        Expand to Translate
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Introduction

Amniocentesis is a prenatal diagnostic test carried out mainly between 14th to 18th week of pregnancy (GA week 14 to 18). Amniotic fluid is taken from the uterus, sent to a diagnostic laboratory and embryonic cells isolated from the amniotic fluid. No anaesthetic is required, and a result is usually obtained in about three to four weeks. When the test is carried out by an obstetrician experienced in the technique, the risk of a miscarriage related to the test is about 1 %. Diagnosis Links: Prenatal Diagnosis | pregnancy test | amniocentesis | chorionic villus sampling | ultrasound | Alpha-Fetoprotein | Pregnancy-associated plasma protein-A | Fetal Blood Sampling | Magnetic Resonance Imaging | Computed Tomography | Non-Invasive Prenatal Testing | Fetal Cells in Maternal Blood | Preimplantation Genetic Screening | Comparative Genomic Hybridization | Genome Sequencing | Neonatal Diagnosis | Category:Prenatal Diagnosis | Fetal Surgery | Classification of Diseases | Category:Neonatal Diagnosis | Placenta - Amnionic Sac

Some Recent Findings

The yield and complications of amniocentesis performed after 24 weeks of gestation "This study assessed the use and complications of late amniocentesis (AC) and analyzed factors that affect complication rate. A retrospective analysis of 167 genetic AC performed after 24 weeks during a 10-year period in two medical centers was conducted. Data regarding the indications for AC, genetic work-up, and pregnancy outcomes were retrieved from patient medical records and telephone-based questionnaires. Mean gestational age (GA) at the time of AC was 31.7 ± 2.7 weeks; 104 procedures were performed at ≤32 weeks, including 24 at ≤30 weeks. The overall pregnancy complication rate occurring at any time after the procedure was 6.6% (11). Of these, 4.8% (8) occurred within a month after AC, including 2.4% (4) that occurred within a week. An additional three occurred after 30 days. There were no differences in the total complication rate and in the rate of specific complications of procedures performed at ≤32 weeks or at ≤30 weeks. Maternal age did not affect outcomes. Genetic testing was abnormal in five cases (3%). Amniocyte culture failed in 3 cases (2.3%), with no technical failures in 52 chromosomal microarray tests. The complication rate of AC performed after 24 weeks was 4.8%, which is significantly higher than that of second trimester AC. GA and maternal age did not affect the complication rate." Metabolomics of Human Amniotic Fluid and Maternal Plasma during Normal Pregnancy "Metabolic profiles of amniotic fluid and maternal blood are sources of valuable information about fetus development and can be potentially useful in diagnosis of pregnancy disorders. In this study, we applied 1H NMR-based metabolic profiling to track metabolic changes occurring in amniotic fluid (AF) and plasma (PL) of healthy mothers over the course of pregnancy. AF and PL samples were collected in the 2nd (T2) and 3rd (T3) trimester, prolonged pregnancy (PP) until time of delivery (TD). ... Lactate to pyruvate ratio was decreased in AF and conversely increased in PL. The results of our study, show that metabolomics profiling can be used to better understand physiological changes of the complex interdependencies of the mother, the placenta and the fetus during pregnancy. In the future, these results might be a useful reference point for analysis of complicated pregnancies." Proteomic Biomarkers in Second Trimester Amniotic Fluid That Identify Women Who Are Destined to Develop Preeclampsia "Using proteomic technology, this study identified protein biomarkers that are differentially expressed in the early second trimester AF from women who subsequently develop preeclampsia compared with women who remained normotensive. Early identification of women at risk of developing preeclampsia will allow clinicians to better optimize maternal and perinatal outcomes." Fatty acid composition of mid-trimester amniotic fluid in women of different ethnicities "DHA did not differ among the ethnic groups or according to pregnancy outcome. A reduced palmitic acid percentage was identified in the six women with preeclampsia. ...Amniotic fluid fatty acid composition differed among the ethnic groups and may influence inflammatory mediator production and susceptibility to preeclampsia." Fetal outcome and amniocentesis results in pregnancies complicated by varicella infection "...In cases of varicella infection during pregnancy, negative studies of amniotic fluid using PCR may contribute to decision making." Difficulties in establishing routine amniocentesis for preterm labor evaluation "The predominant reasons for not performing an amniocentesis were patient refusal and provider discomfort. In conclusion, implementation of amniocentesis to evaluate for subclinical infection/inflammation in the setting of preterm labor (PTL) or preterm premature rupture of membranes (PPROM) proved difficult, as only 7 of 59 (11.9%) patients admitted with these diagnoses actually received an amniocentesis."

More recent papers

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Testing Comparison

A Chochrane review (2003) comparing prenatal diagnosis showed that early amniocentesis is not a safe as mid-trimester amniocentesis or chorionic villus sampling, because of increased pregnancy loss and the increased risk of Talipes equinovarus.

Cells floating in the fluid can be isolated for genetic analysis and the amniotic fluid can also be often assessed for both quality and quantity. The amniotic fluid volume increases as the fetus grows and rate of change varies during the pregnancy.

• up to 8 weeks - increases at the rate of 10 ml/week
• 8 to 13 weeks - increases at the rate of 25 ml/week
• 13 to 21 weeks - increases at the rate of 60 ml/week
• 21 to 33 weeks - amniotic volume increase starts decreasing and eventually plateaus.
• 34 weeks (GA) - peaks at about 800 mL.
• 40 weeks (GA) - about 600 mL at term.

Fluid Facts

• Circulated by fetal inhaling and swallowing.
• Replaced by fetal exhalation and urination.
• Magnesium low levels associated with preeclampsia and diabetes.
  • normal magnesium value at 16 weeks (GA) is 1.65 ± 0.16 mg/dL in amniotic fluid and 1.97 ± 0.23 mg/dL in serum.

Amniotic Fluid Stem Cells

It has been shown that human amniotic fluid stem cells (hAFSCs) can be retrieved directly from a small amount of mid-term pregnancy amniotic fluid that can be obtained at the time of diagnostic amniocentesis. These are generally considered as mesenchymal stem cells.

Links: Stem Cell

References

Reviews

Evans MI, Wapner RJ. Invasive prenatal diagnostic procedures 2005. Semin Perinatol. 2005 Aug;29(4):215-8.

Ball RH. Invasive fetal testing. Curr Opin Obstet Gynecol. 2004 Apr;16(2):159-62.

Articles

<pubmed>21516255</pubmed>

Search PubMed

April 2010

• Amniocentesis - All (9443) Review (801) Free Full Text (692)

Search PubMed: Amniocentesis | Amniotic fluid

Prenatal Diagnosis Terms

• ART - Assisted Reproductive Technology a general term to describe all the clinical techniques used to aid fertility.

• blastomere biopsy - An ART preimplantation genetic diagnosis technique carried out at cleavage stage (day 3), excluding poor quality embryos, detects chromosomal abnormalities of both maternal and paternal origin. May not detect cellular mosaicism in the embryo.

• blastocyst biopsy - An ART preimplantation genetic diagnosis technique carried out at blastocyst stage (day 4-5), removes several trophoblast (trophoderm) cells, detects chromosomal abnormalities of both maternal and paternal origin and may detect cellular mosaicism.

• cell-free fetal deoxyribonucleic acid - (cfDNA) refers to fetal DNA circulating and isolated from the plasma portion of maternal blood. Can be performed from GA 10 weeks as a first-tier test or as a second-tier test, with women with increased probability on combined first trimester screening offered cfDNA or diagnostic testing.

• false negative rate - The proportion of pregnancies that will test negative given that the congenital anomaly is present.

• false positive rate - The proportion of pregnancies that will test positive given that the congenital anomaly is absent.

• free β human chorionic gonadotrophin - beta-hCG subunit of hCG used as a diagnostic marker for: early detection of pregnancy, Trisomy 21, spontaneous abortion, ectopic pregnancy, hydatidiform mole or choriocarcinoma.

• multiples of the median - (MoM) A multiple of the median is a measure of how far an individual test result deviates from the median and is used to report the results of medical screening tests, particularly where the results of the individual tests are highly variable.

• negative predictive value - The probability that a congenital anomaly is absent given that the prenatal screening test is negative.

• Non-Invasive Prenatal Testing - (NIPT) could refer to ultrasound or other imaging techniques, but more frequently used to describe analysis of cell-free fetal DNA circulating in maternal blood.

• polar body biopsy - (PB biopsy) An ART preimplantation genetic diagnosis technique that removes either the first or second polar body from the zygote. As these are generated by oocyte meiosis they detects chromosomal abnormalities only on the female genetics.

• positive predictive value - The probability that a congenital anomaly is present given that the prenatal screening test is positive.

• pre-implantation genetic diagnosis - (PGD, pre-implantation genetic screening) a diagnostic procedure for embryos produced through Assisted Reproductive Technology (ART, in vitro fertilisation, IVF) for genetic diseases that would generate developmental abnormalities or serious postnatal diseases.

• prenatal screening sensitivity - (detection rate) The probability of testing positive on a prenatal screening test if the congenital anomaly is present.

• prenatal screening specificity - The probability of testing negative on a prenatal screening test if the congenital anomaly is absent.

• quadruple test (maternal serum testing of a-fetoprotein Template:AFP, free B-hCG or total hCG, unconjugated estriol, and inhibin A) is a fetal chromosomal anomaly test usually carried out later in pregnancy (GA 14 to 20 weeks).

• single nucleotide polymorphisms - (SNPs) the variation in a single DNA nucleotide that occurs at a specific position in the genome.

• triple test - (maternal serum testing of a-fetoprotein Template:AFP, free B-hCG or total hCG, and unconjugated estriol) is a fetal chromosomal anomaly test usually carried out later in pregnancy (GA 14 to 20 weeks).

External Links

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• NIH Medline Plus Amniocentesis | Interactive Tutorial

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Cite this page: Hill, M.A. (2024, April 16) Embryology Amniocentesis. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Amniocentesis

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© Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G