Comparison · Pregnancy Smart
Prenatal microarray vs karyotype
How do the options compare?
Compare the size and type of DNA change each analysis can find, laboratory platform, uncertain results, sample requirements, ultrasound findings, and family chromosome history.
| Option | Studied pregnancy dose | Guideline support | Notes |
|---|---|---|---|
| Chromosomal microarray | Laboratory analysis of a CVS or amniocentesis sample; no medication dose | Detects chromosome gains or losses, including many changes too small for a standard karyotype. Particularly useful when a fetal structural anomaly is present. | May return uncertain findings. Capabilities differ between SNP and comparative-genomic-hybridization arrays; balanced rearrangements and single-gene changes may be missed. |
| Conventional karyotype | Microscopic chromosome analysis of a diagnostic cell sample; no medication dose | Shows chromosome count and larger structural arrangements, including balanced rearrangements that a copy-number array may not reveal. | Usually cannot identify small deletions or duplications visible only at microarray resolution. Family chromosome history may make the structural information particularly relevant. |
- A karyotype examines chromosome number, size, and structure. Prenatal samples can come from placental tissue collected by CVS or fetal cells in amniotic fluid. The sampling procedure and the laboratory analysis are separate decisions. 1
- In a prospective study enrolling 4,406 patients at 29 centers, microarray found clinically relevant deletions or duplications after a normal karyotype in 6.0% of pregnancies with structural anomalies and 1.7% with age-related or positive-screen indications. These selected groups and older platforms do not define an individual probability today. 2
- A laboratory series of 3,223 prenatal samples found that 2.5% of the subgroup eligible for either microarray or karyotype had clinically significant abnormalities that karyotyping would miss. This referred testing population was not a random sample of all pregnancies. 3
- Microarray capability depends on the platform. SNP-based arrays can identify triploidy, whereas comparative-genomic-hybridization arrays generally cannot. Routine microarray can miss balanced rearrangements, single-gene changes, and low-level mosaicism, so a normal result does not exclude every genetic condition. 4
- A microarray can report a DNA change whose clinical significance is uncertain. Interpretation may use parental testing, ultrasound findings, and updated databases. Pretest counseling should explain uncertain or incidental findings and the limits of predicting severity before a sample is analyzed. 4
Which option makes sense?
Choose the laboratory analysis with the prenatal genetics team. Microarray adds resolution for DNA gains and losses; karyotyping adds structural information. The right combination follows the clinical question and informed preferences.
Disclosure: Pregnancy Smart is a supplement maker. The options compared above sit outside our own product line; this page describes their pregnancy evidence on its own merits.
Frequently asked questions
What can prenatal microarray find that a karyotype misses?
Microarray can find small missing or extra DNA segments, often called microdeletions and microduplications. A standard karyotype sees larger chromosome changes. The additional yield depends on the ultrasound findings, testing indication, array coverage, and laboratory reporting policy.
Are microarray and karyotype the same as NIPT?
No. NIPT screens DNA fragments in maternal blood to estimate the chance of selected chromosome conditions. Prenatal microarray and karyotyping analyze a diagnostic sample obtained through CVS or amniocentesis. Each still has a defined scope; neither is a test for every possible condition.
Does choosing microarray mean I need another amniocentesis?
Not necessarily. A laboratory may be able to use material from the same diagnostic sampling procedure for more than one analysis, as occurred in the prospective comparison study. Ask about sample quantity, storage, cell culture, and which analyses were ordered before assuming another procedure is needed.
Why might a genetics team recommend microarray after an abnormal ultrasound?
A structural anomaly increases the chance that a clinically relevant small DNA imbalance will be found despite a normal karyotype. Specialist guidance favors microarray in this setting when diagnostic testing is chosen. Counseling should still address family history and whether another type of analysis is also needed.
Can microarray find a balanced chromosome translocation?
A balanced rearrangement moves chromosome material without a detectable net gain or loss, so routine microarray may miss it. Karyotyping can show the arrangement. Tell the genetics team about a known parental translocation, previous chromosome findings, or a relevant reproductive history.
Can microarray detect triploidy?
The platform matters. SNP-based microarrays can identify the extra chromosome set through allele patterns, while comparative-genomic-hybridization arrays generally cannot. The older comparison trial used methods that missed triploidy, so its result should not be applied to every current array. Ask which technology the laboratory uses.
What does a variant of uncertain significance mean before birth?
It means the laboratory does not yet have enough evidence to classify a DNA finding confidently. It is not automatically evidence that the fetus will be affected. A genetics specialist may review parental results, imaging, and databases; inherited findings also need interpretation rather than automatic reassurance.
Does a normal microarray or karyotype guarantee a healthy baby?
No. A normal result addresses the changes the selected analysis can detect. Many single-gene conditions, some mosaic findings, and nongenetic causes of birth differences fall outside that scope. Continue recommended ultrasound care and discuss any new finding with the prenatal and genetics teams.
Related in the library
References
MedlinePlus · https://medlineplus.gov/lab-tests/karyotype-genetic-test/
Chromosomal Microarray versus Karyotyping for Prenatal Diagnosis
PMC · https://pmc.ncbi.nlm.nih.gov/articles/PMC3549418/
ACOG and SMFM guidelines for prenatal diagnosis: Is karyotyping really sufficient?
PMC · https://pmc.ncbi.nlm.nih.gov/articles/PMC5900922/
Prenatal Diagnosis by Chromosomal Microarray Analysis
PMC · https://pmc.ncbi.nlm.nih.gov/articles/PMC5856154/
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