Best Specimen for Chromosomal Analysis in Stillbirth
Amniotic fluid (Option B) is the best specimen for chromosomal analysis in a stillbirth case, as it contains viable fetal cells shed from multiple fetal tissues and provides the most reliable source for karyotyping with high success rates. 1
Rationale for Amniotic Fluid as the Optimal Choice
Amniotic fluid contains fetal cells shed from the fetal skin, bladder, gastrointestinal tract, and amnion, making it an excellent source for chromosomal analysis in stillbirth cases. 1
Amniotic fluid specimens can be reliably analyzed between 13 to 25 weeks of gestation, providing consistent diagnostic yield throughout the gestational period when stillbirths occur. 1
The cellular content in amniotic fluid allows for successful culture and karyotyping, with established protocols for specimen handling and processing that maximize diagnostic success. 2
Why Other Options Are Less Optimal
Umbilical Cord Sampling (Option A)
Fetal cord blood is the standard specimen for postnatal chromosomal analysis after delivery, not specifically for stillbirth evaluation where the fetus is already deceased. 3
Blood specimens may have reduced viability in stillbirth cases due to cellular degradation after fetal demise, potentially compromising culture success.
Fetal Cord Blood (Option C)
While fetal cord blood is preferred for postnatal karyotyping in live births, it faces the same limitations as umbilical cord sampling in stillbirth scenarios where cellular viability is compromised. 3
Maternal cord blood contamination is a critical concern, as it would reflect maternal chromosomes rather than fetal chromosomes, making it useless for fetal genetic diagnosis. 3
Placental Tissue (Option D)
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. 2
Confined placental mosaicism is a major limitation, as chromosomal abnormalities detected in placental tissue may not represent the true fetal karyotype. 3
Extensive placental tissue testing is not recommended for routine clinical care due to the risk of discordant results between placental and fetal chromosomes. 3
Technical Considerations for Stillbirth Specimens
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. 2, 1
If amniotic fluid is unavailable, skin fibroblasts from the fetus are particularly valuable for detecting mosaicism that may not be present in other tissues, though this requires delivery and tissue collection. 1
Fresh tissue transport requires appropriate handling with ice or dry ice if previously frozen, while avoiding prolonged formalin fixation that reduces success rates. 2, 1
Common Pitfalls to Avoid
Do not rely solely on placental tissue due to confined placental mosaicism, which can lead to false positive or false negative results. 3
Avoid specimens like hair, vitreous fluid, synovial fluid, and urine as they yield low amounts of DNA and have high contamination risk. 2
When collecting skin specimens, clean with alcohol only—never use iodine-containing compounds, as iodine inhibits cell culture growth. 1