Audit of a screening service for fetal abnormalities using early ultrasound scanning and maternal serum α-fetoprotein estimation combined with selective detailed scanning

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Abstract

The objective of the study was the evaluation of a screening service for fetal abnormality using early ultrasound scanning to date and establish viability of the pregnancy combined with maternal serum α-fetoprotein estimation at 16 weeks and thereafter selective detailed scanning at 18–20 weeks based on clinical indication. The study was designed to be retrospective, emphasizing the possibility of diagnosis. Early scans were performed by radiographers and radiologists, detailed ones by radiologists and obstetricians with subspecialty training in prenatal diagnosis. The study was carried out in the ultrasound department of a large University Hospital. The subjects studied were all cases of abnormality identified pre- or postnatally in women delivering in the hospital over 4 years and to whom the screening service applied. Information was obtained from ultrasound and maternity records, birth notifications, pathology and autopsy reports and a special needs register. Cases were classified as not detectable, potentially detectable and usually detectable. Major fetal anomalies numbered 255 (total deliveries 19 497), a prevalence of 1.3%; 130 (51%) were diagnosed by ultrasound with 64%; before 24 weeks and 36% later. Eleven chromosomal anomalies (4%) were diagnosed by genetic methods and 114 (45%) anomalies were not diagnosed antenatally. The sensitivity of the program was 37% before 24 weeks. Chromosomal anomalies, lesions of the central nervous system and cardiac defects were most common, followed by lesions of the gastrointestinal and urinary tracts. A large proportion of the detected and detectable anomalies were lethal. The implementation of a policy of routine scans at 18–20 weeks for fetal abnormality would be justified if it led to improved obstetric decision-making, reduction in child handicap and less parental suffering. A routine stun applied to our population might not have achieved these except in a comparatively small number of cases. Copyright © 1995 International Society of Ultrasound in Obstetrics and Gynecology

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