Feasibility and acceptance of screening for fragile X mutations in low-risk pregnancies.

Fragile X syndrome is the second leading cause of mental retardation after Down syndrome. Most women carriers of the fragile X mutation are unaware of their condition. We critically evaluated whether screening pregnant women at low risk for FMR1 mutation would be feasible as a routine part of antenatal care in general practice. We also studied acceptance and attitudes to gene testing. From July 1995 until December 1996, a carrier test was offered at the Kuopio City Health Centre free of charge to all pregnant women in the first trimester following counselling given by midwives on fragile X syndrome. All women found to be carriers of FMR1 gene mutations underwent detailed genetic counselling and were offered prenatal testing. Attitudes towards the gene test were elicited by questionnaire. Most pregnant women (85%) elected to undertake the gene test. Six women were found to be carriers (a rate of 1 in 246), and all subsequently accepted prenatal testing. Three foetuses had a normal FMR1 gene, one had a large premutation, one a 'size mosaic' mutation pattern, and another a full mutation. This observational and interventional study demonstrates that antenatal screening provides an effective way of identifying carriers and incorporating prenatal testing into this process.