Amniotic fluid culture failure: clinical significance and association with aneuploidy

OBJECTIVE: To characterize clinical aspects associated with second-trimester amniotic fluid (AF) culture failure. METHODS: The reports of all amniocentesis samples received in our cytogenetic laboratory over a 9-year period were reviewed to identify cases in which culture failure of amniocytes occurred. Medical records were then reviewed for the prenatal ultrasonographic findings, karyotype when available, and clinical outcome. RESULTS: During the study period, 4134 second-trimester AF samples were processed, of which 42 (1%) failed to yield a result. Complete information was available in 41 pregnancies, which are the basis of this report. Karyotyping was done ultimately in 32 of the 41 cases (78%). The frequency of an abnormal karyotype was greater in those pregnancies in which AF culture failure occurred in comparison with those in which a cytogenetic result was obtained (six of 32 [19%] versus 149 of 4092 [4%], P < .001). There was also a greater prevalence of fetal abnormalities detected on prenatal ultrasonography, mainly oligohydramnios, hydrops, and fetal growth restriction, in the AF culture failure group compared with the successful AF culture group (17 of 41 [41%] versus 351 of 4092 [9%1, P < .001). All chromosomally abnormal fetuses had anomalies detected at ultrasonography. CONCLUSION: Our findings confirm the previously reported association between karyotype abnormality and AF culture failure, but suggest that this association is probably due to fetal anomalies, detectable on prenatal ultrasonography, that lead to decreased fetal cell shedding.