Best Sample for Chromosomal Analysis in Fetal Demise
When there is no fetal heartbeat, placental tissue (fresh, not formalin-fixed) is the best specimen for chromosomal analysis, followed by fetal skin fibroblasts if fresh tissue transport is available. 1
Specimen Collection Priority in Fetal Demise
First-Line Specimen: Fresh Placental Tissue
- Fresh placental tissue should be collected immediately after delivery and transported appropriately to the laboratory 1
- This is the preferred specimen because it provides viable cells for culture and chromosomal analysis in cases of fetal demise 1
- Critical caveat: Avoid prolonged formalin fixation, as formalin-fixed paraffin-embedded tissue has very low success rates in many laboratories 1
- Transport fresh tissue on ice, or with dry ice if previously frozen 1
Second-Line Specimen: Fetal Skin Fibroblasts
- Cultured fibroblasts from fetal skin can be used if fresh tissue transport is available 1
- Clean the skin with alcohol only—never use iodine-containing compounds, as iodine inhibits cell culture growth 1
- Skin fibroblasts are particularly valuable for detecting mosaicism that may not be present in other tissues 2
Why Other Options Are Inappropriate
Umbilical Cord Blood (Option A & C)
- Fetal cord blood is the standard specimen for postnatal chromosomal analysis when the infant has been delivered alive and requires karyotyping 3
- In the context of fetal demise (no heartbeat), cord blood is not viable for culture and analysis
- The American College of Medical Genetics recommends cord blood specifically for postnatal analysis in live births, not for demised fetuses 3
Amniotic Fluid (Option B)
- Amniotic fluid is a prenatal specimen collected before delivery via amniocentesis 3
- After fetal demise and delivery, amniotic fluid is no longer accessible or relevant for testing 3
- This option would only be appropriate if the demise was diagnosed before delivery and amniocentesis was performed at that time
Critical Technical Considerations
Timing and Documentation
- Collect specimens as soon as possible after diagnosis of demise 1
- Document the time of collection after death and storage conditions, as laboratories may have acceptance criteria based on these factors 1
Specimens to Avoid
- Hair, vitreous fluid, synovial fluid, and urine are not suitable due to low DNA yield and high contamination risk 1
- Formalin-fixed tissue should be avoided for primary chromosomal analysis due to poor success rates 1
Clinical Context
The question specifically asks about chromosomal analysis when there is no heartbeat, indicating fetal demise. In this scenario, the standard prenatal (amniotic fluid) and postnatal live-birth specimens (cord blood) are not applicable. Fresh placental tissue becomes the specimen of choice because it provides the best opportunity for successful cell culture and karyotyping in the setting of fetal death 1.