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Understanding Genetic Miscarriage Tests: Alternatives to Traditional Methods

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A pregnancy loss can be devastating, and moving forward can be difficult especially if feelings of guilt and shame enter the grieving process. Many find comfort in learning the cause of their miscarriage.1 The majority of miscarriages are caused by chromosomal abnormalities.2 A genetic miscarriage test, such as karyotyping or AnoraTM, can help you find the answers you need to move forward. 

What Is a Chromosomal Abnormality?

A normal human cell has 46 chromosomes arranged in 23 pairs. Each parent contributes one of each chromosome in a pair from their sperm or egg cells. However, random errors can occur in sperm or egg cells that lead to too many, too few, or missing pieces of chromosomes. These errors are called chromosomal abnormalities. Since chromosomes hold our DNA, the instructions for how our bodies grow and function, a chromosomal abnormality can make it impossible for a fetus to develop past a certain point. If this happens, a miscarriage will occur, usually in the first trimester.3

Chromosomal abnormalities are the most common cause of miscarriage.2 Most of the time they are completely random, unpreventable, and unlikely to repeat in a future pregnancy. In very rare cases, one parent could be a carrier for an abnormality that increases the chance of miscarriage or a future pregnancy with a chromosome disorder.

What Is Karyotyping?

Karyotyping is a type of genetic test that can detect some kinds of chromosomal abnormalities. To perform a karyotype miscarriage test, cells from miscarriage tissue must be grown in the lab. When the cells reach a certain stage, the chromosomes are extracted and stained, and then a microscope is used to identify and count them.

While karyotyping can find chromosomal abnormalities, the process can take as long as 2-5 weeks and fails 10-40% of the time due to problems growing the cells in a lab.4 Karyotyping often cannot identify whether small pieces of chromosomes are missing or duplicated. It can give false results if there are maternal cells mixed in with the miscarriage tissue, called maternal cell contamination (MCC). Karyotyping cannot tell doctors which parent an abnormal chromosome came from and it cannot identify uniparental disomy (UPD), a condition where both copies of a particular chromosome pair came from only one parent. Triploidy and UPD from the father cause molar pregnancy and increase the risk for serious maternal health complications, and cannot be diagnosed by karyotype. Finally, karyotyping can only be performed on fresh miscarriage tissue and will not work with paraffin-preserved tissue from a past loss.

How Is Anora Different?

Anora’s proprietary technology uses single nucleotide polymorphisms (SNPs), unique genetic markers that offer deeper insights into the potential genetic causes of a miscarriage. Anora’s technology means that in addition to everything karyotyping does, it can tell whether a chromosome has lost or gained small extra pieces. Using Natera’s patented Parental SupportTM Technology, Anora can detect or rule out maternal cell contamination (MCC), identify uniparental disomy (UPD), and determine the parental origin of an abnormality. Anora results can guide follow-up testing for parents, which may help identify the rare cases in which a parent carries an abnormality that could impact future pregnancies.

Above all, Anora’s technology is reliable. It does not require growing cells in the lab—this means >99% success in obtaining results and rapid turnaround time, with a report available approximately one week after samples are received at Natera. It also means that Anora can be performed for miscarriages that occurred years ago, as long as paraffin-preserved tissue was saved by a doctor.

Anora Vs. Karyotyping

Karyotype Anora
Identify missing or extra chromosomes
Identify small missing or extra pieces of chromosomes X
Rule out MCC X
Identify UPD X
Available for past miscarriages X
Results provided 60-90% of the time >99% of the time
Report available 2-5 weeks 1 week

Learn More About Anora

Anora can help you find answers after a miscarriage. Visit to learn more about genetic miscarriage testing.

Learn More

If you have questions about Natera billing, please call the Natera billing phone number at 1-844-384-2996 ( (8 am-7 pm CT M-F).


1Bardos et al. Obstet Gynecol. 2015; 125(6): 1313-20.

2Practice Committee of the American Society for Reproductive Medicine. Fertil Steril. 2012;98(5):1103-11.

3Mukherjee et al. Am J Epidemiol. 2013; 177(11):1271-8.

4Levy et al., Obstet Gynecol. 2014 Aug; 123 (2 pt1): 202-9.

*Anora has been developed and its performance characteristics determined by the CLIA-certified laboratory performing the test. The test has not been cleared or approved by the US Food and Drug Administration (FDA). CAP accredited, ISO 13485 certified, and CLIA certified. © 2021 Natera, Inc. All Rights Reserved.