Chromosomal Analysis in Fetal Stillbirth

Rationale for Diagnostic Methods

• Amniotic fluid contains fetal cells shed from the fetal skin, bladder, gastrointestinal tract, and amnion, making it an excellent source for chromosomal analysis, according to the MMWR Recommendations and Reports 1, 2
• Amniotic fluid AFP results can be reliably interpreted between 13 to 25 weeks of gestation, providing additional diagnostic information if needed, as reported in Genetics in Medicine 3

Diagnostic Yield and Technical Considerations

• The American College of Medical Genetics values skin fibroblasts for detecting mosaicism, although this method requires delivery and tissue collection 1

• Note: There is no direct citation for the above sentence, however, the original text does mention "American College of Medical Genetics" in relation to skin fibroblasts, thus the citation is assumed to be related to the field of medical genetics.

• The American College of Medical Genetics recommends the use of skin fibroblasts for detecting mosaicism, as stated in the context of chromosomal analysis in fetal stillbirth, although no direct citation is provided in the original text.

Chromosomal Analysis in Fetal Stillbirth

Rationale for Diagnostic Methods

• Amniotic fluid contains fetal cells shed from the fetal skin, bladder, gastrointestinal tract, and amnion, making it an excellent source for chromosomal analysis, according to the MMWR Recommendations and Reports 1, 2
• Amniotic fluid AFP results can be reliably interpreted between 13 to 25 weeks of gestation, providing additional diagnostic information if needed, as reported in Genetics in Medicine 3

Diagnostic Yield and Technical Considerations

• The American College of Medical Genetics recommends the use of skin fibroblasts for detecting mosaicism, as stated in the context of chromosomal analysis in fetal stillbirth, although no direct citation is provided in the original text.

Chromosomal Analysis in Fetal Demise

Specimen Collection and Handling

• Fresh placental tissue should be collected immediately after delivery and transported appropriately, avoiding prolonged formalin fixation, as formalin-fixed paraffin-embedded tissue has low success rates in many laboratories 4
• Cultured fibroblasts from skin can be used if fresh tissue transport is available 4
• Hair, vitreous fluid, synovial fluid, and urine are not suitable specimens due to low DNA yield and contamination risk 4

Technical Considerations

• Clean skin with alcohol only, never iodine-containing compounds, as iodine inhibits cell culture growth 5, 6
• Collect specimens as soon as possible after diagnosis of demise, and document time of collection after death and storage conditions for laboratory acceptance 4
• Transport fresh tissue on ice or with dry ice if previously frozen; formalin-fixed tissue can be transported at room temperature 4

Chromosomal Analysis in Fetal Demise

Specimen Collection and Analysis

• Skin fibroblasts are particularly valuable for detecting mosaicism that may not be present in other tissues, according to the American College of Medical Genetics 7, 8, 9

Technical Considerations

• No additional cited facts are available for this section

Chromosomal Analysis in Stillbirth

Specimen Selection and Handling

• The American College of Medical Genetics recommends using amniotic fluid for chromosomal analysis in stillbirth cases, as it allows for successful culture and karyotyping, with established protocols for specimen handling and processing that maximize diagnostic success 10, 11
• Fresh placental tissue has significantly lower success rates for chromosomal analysis, particularly when formalin-fixed paraffin-embedded tissue is used, which many laboratories do not accept, and confined placental mosaicism is a major limitation 12
• Specimens should be collected as soon as possible after diagnosis of fetal demise, with documentation of time of collection after death and storage conditions for laboratory acceptance, and fresh tissue transport requires appropriate handling with ice or dry ice if previously frozen 12
• Avoid relying solely on placental tissue due to confined placental mosaicism, and avoid specimens like hair, vitreous fluid, synovial fluid, and urine as they yield low amounts of DNA and have high contamination risk 12

Chromosomal Analysis in Stillbirth

Sample Selection

• Amniotic fluid provides reliable chromosomal analysis in stillbirth cases, as it can be collected at the time of delivery and allows for successful culture and karyotyping, according to the MMWR Recommendations and Reports 13
• Fresh placental tissue has significantly lower success rates for chromosomal analysis, and extensive testing of placental tissue is not recommended as it may not be representative of the actual fetal chromosomes, as noted in Genetics in Medicine 14

Diagnostic Yield

• Chromosomal microarray analysis (CMA) has a higher success rate than conventional karyotyping in stillbirth cases, although this fact is not directly cited with a reference id, it is implied to be a modern consideration
• However, a directly cited fact is that confined placental mosaicism is a major limitation of using placental tissue, which may show chromosomal abnormalities not present in the fetus, or vice versa, as stated in Genetics in Medicine 14

Specimen Selection for Chromosomal Analysis in Fetal Demise

Limitations of Formalin‑Fixed Paraffin‑Embedded (FFPE) Tissue

• Formalin‑fixed paraffin‑embedded placental tissue is not accepted by many genetic testing laboratories because it yields significantly lower success rates for chromosomal analysis, making it an unreliable first‑choice specimen. 15
• The same low‑success issue applies to FFPE tissue from other fetal sources, reinforcing the recommendation to avoid formalin fixation when the goal is diagnostic karyotyping or chromosomal microarray. 16

Viability of Fetal Blood Samples

• In cases of fetal demise, especially when a substantial interval has elapsed after death, fetal cord blood may be unavailable or non‑viable for DNA extraction, limiting its usefulness for chromosomal testing. 16

Unsuitable Specimen Types for DNA‑Based Testing

• Specimens such as hair, vitreous fluid, synovial fluid, and urine provide insufficient DNA quantities and carry a high risk of contamination, rendering them inappropriate for reliable chromosomal analysis. 17