1992, The British Journal of Radiology, 65, 564-569 Routine radiographer screening for fetal abnormalities by ultrasound in an unselected low risk population By 'Isabel M. Shirley, FRCR, Fiona Bottomley, DMU and Victor P. Robinson, MRCOG The Hillingdon Hospital, Uxbridge, Middlesex UB8 3NN, UK Based on a paper presented at the BMUS 23rd Annual Meeting in Bournemouth, on 10-12 December 1991 Keywords: Ultrasound screening, Fetal abnormalities, Radiographers Abstract. A screening programme for fetal abnormalities began at The Hillingdon Hospital in July 1986. Second trimester ultrasound scans are performed by radiographers. A combined prospective and retrospective study of the ultrasound findings and outcome in all pregnancies delivered in 1989-1990 was undertaken. 6412 babies were born during this period, of whom 6183 (96%) were examined by ultrasound in the second trimester; 29 pregnancies were terminated for fetal abnormality. Of the 89 fetuses who were abnormal at birth or at induced termination of the pregnancy (1.4%), 84 were scanned in the second trimester. In 51 cases the abnormality was detected before 22 weeks gestation (sensitivity, 60.7%). 56 of these 84 abnormal fetuses scanned had potentially lethal or major handicapping abnormalities of which 41 were detected by ultrasound before 22 weeks gestation (sensitivity, 73%). There was one false positive diagnosis of abnormality which did not affect outcome. 6352 babies were normal at delivery or on discharge from hospital (specificity, 99.98%). About 2% of newborn infants have congenital or gene- tically determined abnormalities (Royal College of Physicians, 1989). The number of such infants born annually in the UK is currently around 14000. In a district general hospital with a delivery rate of 3000 babies per annum, approximately 60 malformed babies can be anticipated each year. Congenital abnormalities acccount for 20-30% of perinatal deaths (Morrison, 1985) and 90% of infants with congenital malforma- tions and chromosome disorders are born to healthy young women with no identifiable risk factors (Royal College of Physicians, 1989). An ultrasound scan is relatively cheap and safe and provides much useful information during pregnancy, including gestational age, number and viability of fetuses and placental position (Royal College of Obstetricians and Gynaecologists, 1984; Wells, 1987). The majority of pregnant women in the UK now receive at least one ultrasound scan, most of which are per- formed by radiographers (Witcombe & Radford, 1986). There have been a number of recent reports of the ability of pre-natal ultrasound to detect fetal abnormali- ties (Nicolaides & Campbell, 1987; Romero etal, 1988; Nyberg et al, 1990). Studies of ultrasound screening of low-risk populations have demonstrated the ability of scanning to detect between 40% and 85% of fetal abnormalities (Campbell & Smith, 1983; Rosendahl & Kivinen, 1989; Saari-Kemppainen etal, 1990; Chitty et al, 1991; Levi et al, 1991). In particular, three studies have shown that 39.4%, 21% and 74.4% respectively of malformations were detected before 24, 23 and 24 weeks of gestation (Rosendahl & Kivinen, 1989; Chitty et al, *Address correspondence to: Isabel M. Shirley, Consultant Radiologist, The Hillingdon Hospital, Uxbridge, Middlesex UB8 3NN. 1991; Levi et al, 1991) thus allowing parents the option of termination of pregnancy. This report gives our experience of prenatal ultra- sound screening of an unselected low risk population in a District General Hospital, the scans being performed by radiographers. Patients and methods Since July 1986 all women booking for ante-natal care and delivery at The Hillingdon Hospital have been offered a second trimester detailed ultrasound scan using standard real-time equipment. No routine bio- chemical screening for fetal abnormality is available. Approximately 3000 women are delivered annually. Scans are performed at 19 weeks gestation by radiogra- phers holding the Diploma of Medical Ultrasound and who have an average of 4 years' experience of obstetric ultrasound. Supervision is given by a consultant Radiologist with wide experience of obstetric ultrasound (I.M.S.). Scans are performed in the ante-natal clinic to an agreed protocol (Table I). Approximately 15 min is available for each scan and allows assessment of fetal gestational age, viability, number and anatomy and placental position. The fetal anatomical check list is detailed in Table I and recorded in the obstetric notes by the radiographer at the time of scanning. It is important to note that during the period of this study only the fetal facial profile was examined to detect severe bilateral facial clefting. In addition, the presence of limbs was confirmed but they were not studied in detail. If the^ fetus is less than 18 weeks gestation on scanning, the patient is recalled for a further scan. When the ana- tomical check cannot be completed for technical reasons, for example unfavourable fetal lie or excessive fetal movement, the patient is recalled during the session 564 The British Journal of Radiology, July 1992
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Related Documents
