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Amniocentesis.jpg Amniocentesis is a prenatal diagnostic test carried out mainly between 14th to 18th week of pregnancy (GA week 14 to 18).

In amniocentesis, 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 can be about 1 %. A recent study of the published literature, showed a procedure-related risk of miscarriage following amniocentesis was 0.35% (95% confidence interval [CI]: 0.07 to 0.63).[1]. A more detailed Cochrane review of amniocentesis and chorionic villus sampling has also bee carried out.[2] This technique has not yet been fully replaced for primary screening by cell-free DNA analysis.[3]

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

  • 5-Year review on amniocentesis and its maternal fetal complications[4] "Amniocentesis is a well-known invasive procedure which is commonly carried out in the second trimester. The indication for amniocentesis varies throughout countries and centers. Despite providing significant prenatal diagnosis; many maternal and fetal complications have been reported from previous studies. Materials and methods This retrospective study aimed to determine the maternal and fetal complications following amniocentesis. This study involved all patients who underwent amniocentesis from January 2012 until June 2017 in a tertiary centre. Maternal age, parity, premorbid medical conditions, amniocentesis indications, gestational age during amniocentesis, karyotyping results, complications during and post procedure and the fetal outcomes were reviewed and analyzed. Results One hundred and fourteen patients' medical records were reviewed and the majority of patients (50.9%) ranged in age from age 30 to 39 years old with mean age of 34.29 years. Amniocentesis was performed during the second trimester in the majority of patients (71.1%). The indications for amniocentesis in this study were polyhydramnios (7.9%), advanced maternal age (9.6%), risk of Down's syndrome (31.6%), increased risk of Patau syndrome (6.1%), increased risk of Edward's syndrome (4.4%) and abnormal fetal ultrasonography (70.2%). Cytogenetics results of amniocentesis were normal in 82 patients (71.9%). The majority of patients (86.0%) had no complications. Two patients (12.5%) had intrauterine death presumed to be procedural related. Conclusion This 5-year retrospective study on amniocentesis procedure showed that the majority of amniocentesis were safe as 86.0% of the patients were free from any complications. Anticipating its complication is important as there is always a risk even though it is a safe procedure in general."
  • Risk of miscarriage following amniocentesis or chorionic villus sampling: systematic review of the literature and updated meta-analysis[5] "A search of MEDLINE, EMBASE, and The Cochrane Library was carried out to identify studies reporting complications following CVS or amniocentesis. Inclusion criteria for the systematic review were studies reporting results from large controlled studies and those reporting data for pregnancy loss prior to 24 weeks' gestation. Study authors were contacted when required to identify additional necessary data. Data for cases that had invasive procedure and control groups were inputted in contingency tables and risk of miscarriage was estimated for each study. Summary statistics based on a fixed- and random-effects model were calculated after taking into account the weighting for each study included in the systematic review. Procedure-related risk of miscarriage was estimated as a weighted risk difference from the summary statistics for cases and controls. Subgroup analysis according to the similarity risk levels in the invasive testing and control groups was performed. Heterogeneity was assessed using Cochrane's Q and I2 statistic. Egger's bias was estimated to assess reporting bias in published studies. Summary statistics for procedure-related risk of miscarriage were graphically represented in forest plots. CONCLUSIONS: The procedure-related risks of miscarriage following amniocentesis and CVS are lower than currently quoted to women. The risk appears to be negligible when these interventions are compared to control groups of the same risk profile."
  • Prenatally Diagnosed Rare Trisomy 16 Mosaicism in Human Amniotic Fluid Cells in the Second Trimester: A Case Report[6] "Although trisomy 16 is commonly detected in spontaneous abortions and accounts for over 30% of cases of autosomal trisomy detected after spontaneous abortion, trisomy 16 mosaicism is rarely detected by amniocentesis in the second trimester. Here, we report a case of level III trisomy 16 mosaicism (47,XX,+16[8]/46,XX[31]) diagnosed by cytogenetic analysis of independently cultured amniotic fluid cells. The female baby was delivered at full term with low birth weight and intrauterine growth retardation, and interestingly, her karyotype was normal (46,XX). Given the difficulty in predicting the outcomes of fetuses with this mosaicism, it is recommended to inform the possibility of mosaicisms including this trisomy 16 mosaicism during prenatal genetic diagnosis and genetic counseling for parents."
  • The yield and complications of amniocentesis performed after 24 weeks of gestation[7] "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."
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Older papers  
  • Metabolomics of Human Amniotic Fluid and Maternal Plasma during Normal Pregnancy[8]"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[9] "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[10] "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[11] "...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[12] "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."

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.[13]

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.[14]

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.[7] These are generally considered as mesenchymal stem cells.

Links: Stem Cell


A typical example of ultrasound guided amniotic fluid sampling (amniocentesis) at 16 weeks of pregnancy (Royal Berkshire, Published on Oct 21, 2013).

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Links: Movie - CVS | YouTube video


First used as a test of fetal sex in 1955Serr DM, Sachs L & Danon M. (1955). The diagnosis of sex before birth using cells from the amniotic fluid (a preliminary report). Bull Res Counc Isr , 5B, 137-8. PMID: 12307916 , two years later in 1957 was then published as a wider prenatal diagnostic test.[15]


  1. Beta J, Lesmes-Heredia C, Bedetti C & Akolekar R. (2018). Risk of miscarriage following amniocentesis and chorionic villus sampling: a systematic review of the literature. Minerva Ginecol , 70, 215-219. PMID: 29161799 DOI.
  2. Alfirevic Z, Navaratnam K & Mujezinovic F. (2017). Amniocentesis and chorionic villus sampling for prenatal diagnosis. Cochrane Database Syst Rev , 9, CD003252. PMID: 28869276 DOI.
  3. Gray KJ & Wilkins-Haug LE. (2018). Have we done our last amniocentesis? Updates on cell-free DNA for Down syndrome screening. Pediatr Radiol , 48, 461-470. PMID: 29550862 DOI.
  4. Jummaat F, Ahmad S & Mohamed Ismail NA. (2019). 5-Year review on amniocentesis and its maternal fetal complications. Horm Mol Biol Clin Investig , 40, . PMID: 31539354 DOI.
  5. Salomon LJ, Sotiriadis A, Wulff CB, Odibo A & Akolekar R. (2019). Risk of miscarriage following amniocentesis or chorionic villus sampling: systematic review of the literature and updated meta-analysis. Ultrasound Obstet Gynecol , , . PMID: 31124209 DOI.
  6. Kim SR, Choi EJ, Kim YJ, Kim TY & Lee YJ. (2018). Prenatally Diagnosed Rare Trisomy 16 Mosaicism in Human Amniotic Fluid Cells in the Second Trimester: A Case Report. Dev Reprod , 22, 199-203. PMID: 30023470 DOI.
  7. 7.0 7.1 Geffen KT, Ben-Zvi O, Weitzner O, Peleg A, Biron-Shental T & Sukenik-Halevy R. (2017). The yield and complications of amniocentesis performed after 24 weeks of gestation. Arch. Gynecol. Obstet. , 296, 69-75. PMID: 28540575 DOI.
  8. Orczyk-Pawilowicz M, Jawien E, Deja S, Hirnle L, Zabek A & Mlynarz P. (2016). Metabolomics of Human Amniotic Fluid and Maternal Plasma during Normal Pregnancy. PLoS ONE , 11, e0152740. PMID: 27070784 DOI.
  9. Oh KJ, Park JS, Norwitz ER, Kim SM, Kim BJ, Park CW, Jun JK & Syn HC. (2012). Proteomic biomarkers in second trimester amniotic fluid that identify women who are destined to develop preeclampsia. Reprod Sci , 19, 694-703. PMID: 22534327 DOI.
  10. Visnjevac J, Mikić AN, Nikolić A & Visnjevac N. (2010). [Comparative analysis of amniotic fluid lamellar body count and foam stability test as indices of fetal lung maturity]. Med. Pregl. , 63, 747-52. PMID: 21553448
  11. Weisz B, Book M, Lipitz S, Katorza E, Achiron R, Grossman Z & Shrim A. (2011). Fetal outcome and amniocentesis results in pregnancies complicated by varicella infection. J Obstet Gynaecol Can , 33, 720-724. PMID: 21749748 DOI.
  12. McIntosh JJ, McHugh K & Haas DM. (2012). Difficulties in establishing routine amniocentesis for preterm labor evaluation. J. Matern. Fetal. Neonatal. Med. , 25, 313-4. PMID: 21663523 DOI.
  13. Alfirevic Z, Sundberg K & Brigham S. (2003). Amniocentesis and chorionic villus sampling for prenatal diagnosis. Cochrane Database Syst Rev , , CD003252. PMID: 12917956 DOI.
  14. Bocos Terraz JP, Izquierdo Álvarez S, Bancalero Flores JL, González López A & Escanero Marcén JF. (2011). Magnesium concentration in amniotic fluid in the early weeks of the second trimester of pregnancy. BMC Res Notes , 4, 185. PMID: 21672230 DOI.
  15. PARRISH HM, LOCK FR & ROUNTREE ME. (1957). Lack of congenital malformations in normal human pregnancies after transabdominal amniocentesis. Science , 126, 77. PMID: 13442649


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.


Fajnzylber E, Hotz VJ & Sanders SG. (2010). An economic model of amniocentesis choice. Adv Life Course Res , 15, 11-26. PMID: 21516255 DOI.

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Search PubMed: Amniocentesis | Amniotic fluid

Prenatal Diagnosis Terms

  • 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.
  • 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).

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Cite this page: Hill, M.A. (2024, May 18) Embryology Amniocentesis. Retrieved from

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