WISSP - Cytogenetic Assessment

Cytogenetic Assessment

In the WiSSP series, 5-10% of all stillborn infants have had chromosomal abnormalities that were the underlying cause of death. In a majority of these infants the specific reason for their stillbirth would not have been determined had samples not been obtained for chromosome analysis. That is, clinical assessment alone is often insufficient to allow recognition of cytogenetic anomalies in stillborn infants. In part this is true because even common cytogenetic aberrations may be more difficult to recognize in preterm fetuses. In part this is because many stillborn infants are sufficiently macerated that recognizing the external manifestations of a chromosomal abnormality is quite difficult. In the past our recommendation was to order Karyotype with reflex to FISH (fluorescence in situ hybridization) in case of tissue culture failure. This can exclude common chromosome abnormalities such as Trisomy 13, 18, 21 or sex chromosome aneuploidy even when there is no growth in culture.

Recently SNP microarray has become the test of choice recommended by The American College of Obstetrics and Gynecology. Because SNP array does not depend on tissue culture, the success rate is over 90% compared to only about 70% for karyotype. SNP array also provides information about subtle chromosome abnormalities (such as deletion 22q11/DiGeorge, Williams syndrome, etc.) not detectable on routine karyotype. We recommend that chromosomal assessment, preferably SNP microarrayt be attempted on every stillborn baby.

In order to maximize yield, appropriate sampling has to be done. Even for SNP array where tissue culture is not required, sampling technique is important. Only a few laboratories can do SNP array on preserved tissues. Please check with the laboratory where you plan to send the specimen for specific requirements. You may also refer to instructions for obtaining and handling specimens from stillborns for chromosome study as well as instructions regarding Placental Sampling on this website.