Understanding the Risks of Amniocentesis: Miscarriage and Effects on the Fetus

What is amniocentesis? Amniocentesis is a method of taking and examining amniotic fluid from the uterus by inserting a needle from the mother's abdominal surface towards the uterus.

Risks of Amniocentesis

Expecting parents may feel both hope and some concerns about their forthcoming child.

As a potential way to alleviate some of these concerns, options such as NIPT (Non-Invasive Prenatal Testing) and amniocentesis are available. Especially the former offers a low-risk diagnosis unlike traditional prenatal testing.

However, undergoing such tests doesn't solely serve as a reassurance.

Depending on the results of NIPT, further testing may be necessary. Let's reconsider the risks of amniocentesis, which is a confirmatory test following NIPT, as well as the potential impact on both the fetus and the mother.

The Importance of Amniocentesis

While NIPT (Non-Invasive Prenatal Testing) may seem like an easily accessible option, there is also the possibility of discovering a fetal condition.

In such cases, parents who had hoped for reassurance by undergoing NIPT may find themselves facing even greater anxiety.

Although false positive results may sometimes occur, it is necessary to undergo amniocentesis, which provides a definitive diagnosis. Unlike NIPT, amniocentesis is a confirmatory test that identifies fetal conditions.

For parents who desire prenatal testing due to reasons such as advanced maternal age, or for those who have received a positive result from NIPT, amniocentesis can be considered as a last resort.

What is Amniocentesis?

Amniocentesis is a procedure where a needle is inserted from the mother's abdominal surface towards the uterus to collect and examine the amniotic fluid inside.
Unlike NIPT (Non-Invasive Prenatal Testing), which examines the mother's blood for information about the fetus's chromosomes and DNA, amniocentesis provides a definitive diagnosis.

The diseases detectable by NIPT and amniocentesis are compared as follows:

NIPT (Non-Invasive Prenatal Testing)

  • ・Trisomy 21 (Down Syndrome)
  • ・Trisomy 18
  • ・Trisomy 13

In unlicensed facilities, the following can also be examined and diagnosed:

  • ・All chromosomes including sex chromosomes
  • ・Sex determination
  • ・Microdeletion syndromes


・General chromosome disorders including the aforementioned conditions.

If NIPT results are positive, it doesn't necessarily mean that all fetuses have chromosomal abnormalities. As mentioned earlier, there is a possibility of false positives even in cases that should be negative, and it's important to identify those who actually have the condition among those who tested positive.

Furthermore, even if the NIPT results are negative, false negatives are possible. Since NIPT is not a definitive diagnosis, there may still be anxiety until the fetus is born.

Amniocentesis itself can usually be done on an outpatient basis and, like NIPT, it is recommended to undergo the test at facilities (hospitals) where pre-test counseling is available.

After disinfecting the abdomen and administering local anesthesia, a thin needle is used to collect amniotic fluid. The time it takes to collect the amniotic fluid is approximately 30 seconds, and then the patient rests while observing the post-test condition for about 1 to 2 hours before returning home.

Since it is a test that involves inserting a needle directly into the abdomen and uterus, after the test, medications such as uterine relaxants and antibiotics may be prescribed.

Results are typically available 2 to 3 weeks later. During this waiting period, despite the significant anxiety, it's advisable to undergo counseling while awaiting the results.

Possible Risks of Amniocentesis

Amniocentesis involves directly inserting a needle into the mother's abdomen to collect amniotic fluid, so it can be said that there is not only physical but also significant psychological burden.

Local anesthesia is used during the puncture, but some individuals still experience pain.

Above all, there are risks associated with amniocentesis.

Risks of the Procedure

  • ・Possibility of fetal miscarriage
  • ・Possibility of diagnosis being inconclusive due to the condition of the collected amniotic fluid (requiring retesting)
  • ・Potential for pain, bleeding, infection, or premature rupture of membranes

Following an amniocentesis procedure, there is a risk of fetal miscarriage.

This occurs at a rate of approximately 0.1% to 0.3% (1 to 3 cases per 1000), although it's uncertain whether these miscarriages are directly linked to the amniocentesis procedure.

It's important to note that miscarriages can occur naturally, independent of any medical procedure.

In fact, approximately 15% of pregnancies confirmed by medical institutions result in miscarriage, indicating that the likelihood of natural miscarriage is statistically higher.

Moreover, while fetal cells are cultured from the collected amniotic fluid for testing, there are instances where these cells fail to proliferate. In cases where chromosome analysis cannot be performed, another amniocentesis may be necessary, but this may coincide with a period where the test cannot be safely conducted.

Amniocentesis is typically performed after the 15th week of pregnancy, varying slightly depending on the facility, usually around the 16th to 17th week. Since it takes 2 to 3 weeks to receive results, scheduling another test afterward can be quite tight.

For individuals who might consider terminating the pregnancy based on the test results, prompt decision-making is crucial.

Additionally, there is a risk of amniotic fluid leakage or premature rupture of membranes due to the amniocentesis procedure.

According to a report from the National Institute of Child Health and Human Development in the United States, out of 1040 cases where amniocentesis was performed, 1.2% (12 cases) experienced amniotic fluid leakage within a week.

However, since measures such as hospitalization can be taken to stop amniotic fluid leakage, the prognosis is generally favorable.

Undergoing proper counseling before amniocentesis is essential, as it's necessary to overcome not only the anxiety associated with awaiting results but also the risks associated with the procedure itself.