Chorion villus sampling for direct chromosomal analysis in a non-teaching hospital

Abstract

The present method of diagnosing chromosomal abnormalities in pregnancy consists of amniocentesis at 16 weeks when desquamated fetal cells are obtained from the liquor and cultured; a chromosome analysis is possible on the cultured cells in 3–4 weeks. This is a well tried method with a low morbidity, the miscarriage rate in experienced hands being as low as 0.3%. The drawback is the gestational age at which it is done and the delay in producing a result. Patients diagnosed as having an abnormality are faced with a termination at 19–20 weeks when the pregnancy is obvious to all and the material mortality of termination may be as high as 0.26 per 1000 as compared to 0.01 per 1000 when performed before 12 weeks (Report on Confidential Enquiries into Maternal Death, 1982). There is also the emotional strain on the patient waiting for the result during the 3–4 weeks as well as the psychological trauma of the termination. Thus, collection of fetal material with chromosome analysis before 12 weeks would greatly reduce the physical as well as mental morbidity to the patient. The development of chorion villus sampling in the United Kingdom at centres like University College (UCH), Kings College Hospital (KCH) and Glasgow for the extraction of DNA for analysis using DNA markers demonstrated the possibility of obtaining early fetal tissue which could be the basis for a direct chromosome analysis and therefore an alternative test to amniocentesis.