Screening for fetal abnormalities and subsequent karyotyping is a significant component of modern antenatal care. However in 1 year a maternity unit will typically only see a few karyotypic abnormalities. We audited data from 2000 to 2009, to discover the number and type of abnormalities, and outcomes for the pregnancies.
Over the 10 years, there were 35 090 deliveries. Screening for fetal chromosomal abnormalities included multiple methods; the triple test, now quad test, first trimester combined testing to detect Down's and the 20 week anomaly scan.
Results There were a total of 1410 (4.2% of the total number of births) karyotyping procedures performed. 1278 (90.6%) were amniocenteses and 132 (9.4%) were CVS. 106 of these procedures (7.5%) (0.3% of all deliveries) revealed a chromosomal or in a minority of cases, DNA abnormality. 26 (19.6%) were diagnosed after CVS and 80 (6.2%) after amniocentesis.
The main indications for karyotyping were:
Conclusion In the group diagnosed with Down's syndrome, only 26 (62%) were diagnosed following a positive result from the specific screening programme.
Six women chose not to terminate their pregnancy. Five had a baby with Down's syndrome and one Turner's syndrome.
Screening for chromosomal abnormalities yields small numbers of abnormalities when compared to the total number of pregnancies.
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