Minimally invasive prenatal diagnosis of inherited disorders employing trophoblastic cells shed into the endocervical canal

Fetal (trophoblastic) cellular elements have been detected in transcervical cell (TCC) samples collected from the uterine cavity and cervical canal of pregnant women between 6 and 15 weeks of fetal gestation. These cells, present in a background of maternal material, have been identified utilising various molecular techniques. Chromosome Y specific DNA sequences have been detected using both fluorescent in situ hybridisation (FISH) and polymerase chain reaction (PCR) assays. Fetal specific short tandem repeat (STR) allele sizes have been identified in TCC samples indicating the presence of fetal DNA. Trophoblast cells have been identified in TCC samples using monoclonal antibodies specific for trophoblast antigens. Using these methods various TCC sampling procedures have been compared for their efficiency of fetal cell retrieval. The safety of TCC sampling has also been assessed by the collection of samples from ongoing pregnancies prior to CVS, and comparison with a control group. The fetal Rh(d) type has been successfully diagnosed from TCC samples collected from Rh(d) negative mothers. Fetal genetic errors have been identified including trisomy 18, trisomy 21, XYY and triploidy. In attempts to identify recessive fetal disorders and X linked diseases, the isolation of trophoblastic elements has been attempted. Numerous methods have been employed to this end including micromanipulation, trophoblast specific mRNA detection, and magnetic activated cell sorting using trophoblast specific antibodies. Multiplex quantitative fluorescent PCR techniques have been developed to test these isolated cell clumps and individual cells for various inherited disorders. These include the detection of sex chromosome complement, chromosome aneuploidies, the delta-F 508 three base pair deletion causing cystic fibrosis, the single base change causing sickle cell anaemia, and a single base change and two deletions causing beta-thalassaemia. To test separated trophoblast cells, and with a view to potential preimplantation diagnosis, large numbers of isolated single cells were tested with these methods and the results assessed