Steve Conway.Jan, 2001.Antenatal diagnosis [online]. Seacroft and St James's University Hospitals, UK. Available from http://www.cysticfibrosismedicine.com
Antenatal diagnosis is possible using chorionic biopsy at around 9 weeks after conception or amniocentesis at about 15 weeks. Parents of a CF child who are planning to have more children and who wish to have antenatal tests performed to determine if the fetus has CF should ensure they have an appointment to see the geneticist before embarking on the new pregnancy.
Chorionic biopsy: Carried out around 9 weeks after conception and will determine whether the embryo has cystic fibrosis; there is the option to terminate the pregnancy. This antenatal test carries a small but definite risk to the baby and should only be performed if discovery of an affected fetus would result in termination.
Amniocentesis: Is done after the 15th week of pregnancy. Fetal cells can be aspirated from the amniotic fluid that surrounds the baby and cultured for chromosome analysis. Results are not available as quickly as with chorionic biopsy, a clear disadvantage if termination is appropriate. There is a very small risk of miscarriage after the test.
Pre-implantation diagnosis: Is at present only available at specialist centres. Eggs and sperm are harvested from prospective parents who have already had a child with cystic fibrosis. Following in-vitro fertilisation, the developing embryos are screened at a very early stage for their CF status. Selected embryos, free of CF, are implanted into the mother's uterus to continue their development.
Antenatal screening: Has been studied both in the hospital antenatal clinic (Brock, 1996; Gilfillan 1999) and general practice (Harris et al, 1992). Couple screening when the parents are notified only if both are found to have a CF mutation appears to be a satisfactory method which avoids unnecessary anxiety (Miedzybrodzka et al, 1995; Murray et al, 1999).
References
Brock DJH. Prenatal screening for cystic fibrosis: 5 years experience reviewed. Lancet 1996; 347: 148-150.
Gilfillan A J, MacKenzie I M, Warner J P, Brock D J H. Antenatal screening for cystic fibrosis: the Edinburgh experience. Netherlands Journal of Medicine, 1999; 54 (Suppl): S32.
Harris HJ, Scotcher D, Craufurd D, Wallace A, Harris R. Cystic fibrosis carrier screening at first diagnosis of pregnancy in general practice (letter). Lancet 1992; 339: 1539
Miedzybrodzka ZH, Hall MH, Mollison J, Templeton A, Russell IT, Dean JCS et al. Antenatal screening for cystic fibrosis: randomised trial of stepwise v couple screening. BMJ 1995; 310: 353-357
Murray J, CuckleH, Taylor G, Littlewood J, Hewison J. Screening for cystic fibrosis. Health Technol Assess 1999; 3(8): 1-104
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