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

  • Metabolomics of Human Amniotic Fluid and Maternal Plasma during Normal Pregnancy[1] "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[2] "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 [3] "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 [4] "...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 [5] "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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Search term: Amniocentesis

Bruno Schaub, Manon Vouga, Fatiha Najioullah, Michèle Gueneret, Alice Monthieux, Caroline Harte, Françoise Muller, Eugénie Jolivet, Clara Adenet, Sophie Dreux, Isabelle Leparc-Goffart, Raymond Cesaire, Jean-Luc Volumenie, David Baud Analysis of blood from Zika virus-infected fetuses: a prospective case series. Lancet Infect Dis: 2017; PubMed 28209336

M Enders, A Daiminger, S Exler, K Ertan, G Enders, R Bald Prenatal diagnosis of congenital cytomegalovirus infection in 115 cases: a 5 years' single centre experience. Prenat. Diagn.: 2017; PubMed 28207161

Sarah Carroll, Craig V Towers, Lynlee Wolfe, Lisa Duncan, Beth Weitz, Stephanie Porter The effect of freezing amniotic fluid on lamellar body count fetal lung maturity testing. Int J Gynaecol Obstet: 2017; PubMed 28178756

Tarja Myntti, Leena Rahkonen, Irmeli Nupponen, Anu Pätäri-Sampo, Minna Tikkanen, Timo Sorsa, Juuso Juhila, Sture Andersson, Jorma Paavonen, Vedran Stefanovic Amniotic Fluid Infection in Preterm Pregnancies with Intact Membranes. Dis. Markers: 2017, 2017;8167276 PubMed 28167848

Xiya Zhou, Lili Sui, Yalan Xu, Yijun Song, Qingwei Qi, Jianguang Zhang, Hongmin Zhu, Huaiyu Sun, Feng Tian, Mengnan Xu, David S Cram, Juntao Liu Contribution of maternal copy number variations to false positive fetal trisomies detected by noninvasive prenatal testing. Prenat. Diagn.: 2017; PubMed 28152582

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.[6]

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.[7]


  1. Magdalena Orczyk-Pawilowicz, Ewa Jawien, Stanislaw Deja, Lidia Hirnle, Adam Zabek, Piotr Mlynarz Metabolomics of Human Amniotic Fluid and Maternal Plasma during Normal Pregnancy. PLoS ONE: 2016, 11(4);e0152740 PubMed 27070784
  2. Kyung Joon Oh, Joong Shin Park, Errol R Norwitz, Sun Min Kim, Byoung Jae Kim, Chan-Wook Park, Jong Kwan Jun, Hee Chul Syn Proteomic biomarkers in second trimester amniotic fluid that identify women who are destined to develop preeclampsia. Reprod Sci: 2012, 19(7);694-703 PubMed 22534327
  3. Jovana Visnjevac, Aleksandra Novakov Mikić, Aleksandra Nikolić, Nemanja Visnjevac [Comparative analysis of amniotic fluid lamellar body count and foam stability test as indices of fetal lung maturity]. Med. Pregl.: 2011, 63(11-12);747-52 PubMed 21553448
  4. Boaz Weisz, Mazal Book, Shlomo Lipitz, Eldad Katorza, Reuven Achiron, Zehava Grossman, Alon Shrim Fetal outcome and amniocentesis results in pregnancies complicated by varicella infection. J Obstet Gynaecol Can: 2011, 33(7);720-4 PubMed 21749748
  5. Jennifer J McIntosh, Katherine McHugh, David M Haas Difficulties in establishing routine amniocentesis for preterm labor evaluation. J. Matern. Fetal. Neonatal. Med.: 2012, 25(3);313-4 PubMed 21663523
  6. Z Alfirevic, K Sundberg, S Brigham Amniocentesis and chorionic villus sampling for prenatal diagnosis. Cochrane Database Syst Rev: 2003, (3);CD003252 PubMed 12917956
  7. Julia Pilar Bocos Terraz, Silvia Izquierdo Álvarez, Jose Luis Bancalero Flores, Angel González López, Jesús Fernando Escanero Marcén Magnesium concentration in amniotic fluid in the early weeks of the second trimester of pregnancy. BMC Res Notes: 2011, 4;185 PubMed 21672230


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.


Eduardo Fajnzylber, V Joseph Hotz, Seth G Sanders An economic model of amniocentesis choice. Adv Life Course Res: 2010, 15(1);11-26 PubMed 21516255

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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 - (cffDNA) refers to fetal DNA circulating and isolated from the plasma portion of maternal blood.
  • 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.
  • 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.
  • single nucleotide polymorphisms - (SNPs) the variation in a single DNA nucleotide that occurs at a specific position in the genome.
Other Terms Lists  
Terms Lists: ART | Birth | Bone | Cardiovascular | Gastrointestinal | Genetic | Hearing | Heart | Immune | Integumentary | Neural | Oocyte | Palate | Placenta | Renal | Spermatozoa | Ultrasound | Vision | Historic | Glossary

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Cite this page: Hill, M.A. 2017 Embryology Amniocentesis. Retrieved February 22, 2017, from

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© Dr Mark Hill 2017, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G