Maternal cell contamination of amniotic fluid cell cultures: results of a U.S. nationwide survey.

Abstract

AbstractA nationwide survey has been carried out to establish the incidence and factors determining maternal cell contamination (MCC) of amniotic fluid cultures. One hundred sixty‐two cytogeneticists and medical geneticists were invited to participate, and data were collected from 71 laboratories, representing 91,131 amniocenteses. The incidence of recognized cases of MCC was 0.148%, of which 0.123% were recognized as an admixture of male and female cells, the latter often being present in multiple cultures. A further 0.025% of cases were ascertained as a result of unexpected pregnancy outcome. In many of these cases where misdiagnosis occurred, a less than optimal number of cells or cultures were analyzed. Since MCC would generally not be recognized when the fetal sex is female, the true incidence of MCC would be approximately twice these values.MCC incidence was 2½ times lower when the first few milliliters of amniotic fluid were not used for cell culture and appeared to be more common when wider gauge needles were used for the amniocentesis. Twenty‐six percent of MCC cases represented referrals for reasons other than advanced maternal age. Approximately 35% of all cases with MCC were those in which the amniotic fluid was bloody. Cultures with MCC appeared to show no unusual growth properties.It is concluded that the most likely source of MCC is from the outgrowth of maternal tissue removed by the needle. Specific recommendations for dealing with MCC are that 1) the first one or two milliliters of amniotic fluid are not used for cell culture, 2) at least 20 cells from two independent cultures are counted wherever possible, 3) parental polymorphisms are studied in cases where a 46,XX and 46,XY admixture is found, and 4) cases referred fo biochemical studies on cultured cells also receive cytogenetic analysis to help rule out the possibility of MCC.