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  • Author: Pedro Roca, MD, MPH, FACOG; Chief Editor: Ronald M Ramus, MD  more...
Updated: Dec 28, 2015


The removal of amniotic fluid by using a needle through the maternal gravid abdomen has been done since 1877. Initially, it was reported as a therapeutic modality to release amniotic fluid from fetuses with polyhydramnios or to help in the management of fetuses affected by rhesus isoimmunization. Subsequently, following the discovery that cultured amniotic fluid cells could be used to obtain fetal karyotype, amniocentesis was and continues to be used for genetic diagnosis. Additionally, it is used for fetal treatment in cases such as polyhydramnios.[1]



Multiple indications for amniocentesis exist. The most common use of amniocentesis is to diagnose fetal chromosomal anomalies after other tests such as ultrasound or biophysical markers have determined a significant likelihood that the fetus will be affected with a chromosomal problem. Other diagnostic tests performed using amniocentesis are determining fetal lung maturity and evaluating alloimmunization. Amniocentesis can also be used to obtain samples to rule out chorioamnionitis in cases in which the clinical picture is unclear, as well as to deliver intra-amniotic dye in cases in which premature rupture of membranes is suspected.[2, 3, 4, 5]

Therapeutic indications for an amniocentesis may include the direct delivery of medications to the unborn fetus and to release intrauterine pressure in the presence of polyhydramnios.


For the most part, amniocentesis is a safe procedure for the mother. As with any procedure involving the skin, an active skin infection on the proposed needle placement site is a fetal and maternal contraindication. Contractions of the uterus are a relative contraindication. Decreased amniotic fluid or anterior placental position may hamper the success of an amniocentesis.[3, 5]


Technical Considerations

Best Practices

Sterility of the procedure is important because skin contaminants can enter the amniotic fluid and create a fetal infection. Before and after the procedure, fetal heart tones should be obtained to demonstrate fetal viability. The value of the procedure should always be weighed against the risks before an amniocentesis is performed.

Procedure Planning

Consent regarding testing, expectations, complications, and limitations should be clear to the mother, including the possibility of fetal puncture with the needle, preterm labor, infection, and miscarriage. Ideally, genetic amniocentesis should be performed at a gestational age early enough to give the patient the choice of termination of pregnancy legally—usually less than 20 weeks—and late enough in the pregnancy to reduce the chances of miscarriage and foot deformities. Therefore, this procedure is safest between 15 and 18 weeks gestation. Amniocentesis for other indications may be performed later in pregnancy.

Complication Prevention

Real-time ultrasound guidance is generally used for amniocentesis. By using ultrasound, the operator can direct the needle directly toward the amniotic fluid and avoid other structures, such as maternal intraperitoneal organs (bowel, bladder), fetus, or placenta. Avoiding passing the needle through the placenta is preferable because this may create bleeding or placental separation. If the clinician cannot avoid placental insertion, take care to avoid the umbilical cord insertion site, placental edges, and large placental blood vessels.

Miscarriage after amniocentesis has been traditionally reported as 1 in 200, but most recent studies report the risk to be 1 in 1,000. Amniocentesis before 15 weeks gestation, use of large needles, multiple attempts, and unrecognized chorioamnionitis postprocedure are risk factors for miscarriage. The risk of talipes equinovarus is elevated if the amniocentesis is performed prior to 15 weeks gestation.[5, 6]

Additionally, maternal viral infections may be transmitted to the fetus via this procedure. The rate of transmission of HIV is associated with the mother not being on antiretrovirals,[7] and the risk of hepatitis B is associated with the maternal viral load at the time of the procedure.[8] Therefore, counseling regarding risk-benefit analysis should occur with those patients before the procedure.



The goal is to obtain a “clear tap,” indicated by return of clear amniotic fluid during the procedure, without inserting the needle through viable maternal and fetal organs, avoiding preterm contractions, and avoiding a miscarriage.

Contributor Information and Disclosures

Pedro Roca, MD, MPH, FACOG Fellow in Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Hershey Medical Center, Pennsylvania State University College of Medicine

Pedro Roca, MD, MPH, FACOG is a member of the following medical societies: American College of Obstetricians and Gynecologists, American Institute of Ultrasound in Medicine, American Medical Association, American Public Health Association

Disclosure: Nothing to disclose.


Serdar H Ural, MD Associate Professor of Obstetrics and Gynecology and Radiology, Director, Division of Maternal-Fetal Medicine, Medical Director, Labor and Delivery Suite, Pennsylvania State University College of Medicine

Serdar H Ural, MD is a member of the following medical societies: American College of Obstetricians and Gynecologists, American Institute of Ultrasound in Medicine, American Medical Association, Association of Professors of Gynecology and Obstetrics, AAGL, Society for Maternal-Fetal Medicine

Disclosure: Received honoraria from GSK for speaking and teaching; Received honoraria from J&J for speaking and teaching.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Chief Editor

Ronald M Ramus, MD Professor of Obstetrics and Gynecology, Director, Division of Maternal-Fetal Medicine, Virginia Commonwealth University School of Medicine

Ronald M Ramus, MD is a member of the following medical societies: American College of Obstetricians and Gynecologists, American Institute of Ultrasound in Medicine, Medical Society of Virginia, Society for Maternal-Fetal Medicine

Disclosure: Nothing to disclose.

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Cross-sectional representation of relationship between fetus, placenta, and amniotic fluid.
Cross-sectional representation of maternal body during amniocentesis.
Amniocentesis is performed by inserting a syringe into the amniotic fluid during real-time ultrasound guidance.
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