Comparison of cytogenetic analyses of amniotic fluid specimens following a diagnosis of intrauterine fetal demise (IUFD) and specimens derived from products of conception (POC)
Successful tissue culture is imperative for cytogenetic analysis. Using data collected at Genzyme Genetics over a 6 year period, 494 amniotic fluid specimens submitted for cytogenetic analysis with a clinical indication of IUFD are compared with 33,976 POC specimens.
A growth success rate of 93.3% in the amniotic fluid specimens was observed, versus an 84% success rate in POC specimens from a variety of tissue types and a large range of gestational ages. Many factors influence successful cell culture growth in POC specimens not relevant to amniotic fluid cultures. In addition to higher growth success, cytogenetic analyses of IUFD amniotic fluid specimens were reported, on average, in 10 days versus 14-28 days for the average POC study. Therefore, collection of amniotic fluid for cytogenetic analysis prior to pregnancy termination might be advantageous when feasible.
The frequencies of chromosomal abnormalities observed in IUFD amniotic fluid studies differ from POC studies. The most common abnormality detected in IUFD studies was monosomy X (32.4%), compared with trisomy 16 (14%) in POC studies. Trisomy 16 was not observed in the IUFD studies. The common trisomies (13, 18, and 21) comprised 52.3% of the IUFD studies, compared with 16.4% in POC studies. These results may reflect differences in the range of gestational ages in POC studies versus the defined range associated with amniocentesis.