The changing prevalence of neural tube defects: a population-based study in the north of England, 1984-96. Northern Congenital Abnormality Survey Steering Group.
Using data from the Northern Congenital Abnormality Survey, we describe trends in the prevalence of neural tube defects (NTDs), maternal age-specific prevalence, outcome of pregnancy and the sensitivity of antenatal diagnosis of NTD-affected pregnancies in the Northern Region during 1984-96. This population-based sample consisted of 934 NTDs: there were 403 (43.1%) with anencephaly, 472 (50.5%) with spina bifida and 59 (6.3%) with encephalocele. The total prevalence at birth was 17.9 per 10,000 births and terminations (95% confidence interval [CI] = 16.7, 19.0) with a significant reduction over time (chi(2) for trend = 7.2; P = 0.007). The overall birth prevalence was 5.6 per 10,000 births [95% CI = 5.0, 6.3]; there was also a significant reduction in birth prevalence with time (chi(2) for trend = 68.3; P < 0.0001). Maternal age-specific prevalence rates decreased with increasing age. The proportion of NTD pregnancies terminated increased from 60.3% (325 cases) during 1984-90 to 78.6% (293 cases) during 1991-96, whereas the proportion of livebirths declined from 31.7% (171 cases) to 15.0% (56 cases) (P < 0.001). The sensitivity of antenatal diagnosis was consistently high for anencephaly (98%) and increased significantly for spina bifida from 60% during 1984-90 to 85% during 1991-96 (P < 0.05). Ascertainment of all cases of NTD in the Northern Region revealed a twofold reduction in birth prevalence between 1984-90 and 1991-96. This has resulted from improvements in the accuracy of antenatal detection of NTD-affected pregnancies with an increase in terminations of pregnancy.
Rankin
J
J
Department of Epidemiology and Public Health, The Medical School, University of Newcastle, Newcastle upon Tyne, UK. j.m.rankin@ncl.ac.uk
Glinianaia
S
S
Brown
R
R
Renwick
M
M
D000328:Adult; D002869:Chromosome Aberrations / Q000000981:diagnostic imaging / Q000453:epidemiology / Q000235:genetics; D025063:Chromosome Disorders; D004739:England / Q000453:epidemiology; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D008423:Maternal Age; D009436:Neural Tube Defects / Q000000981:diagnostic imaging / Q000453:epidemiology* / Q000235:genetics; D011159:Population Surveillance; D011247:Pregnancy; D011256:Pregnancy Outcome; D015995:Prevalence; D016216:Ultrasonography, Prenatal