Impact of Prenatal Screening and Diagnosis on the Epidemiology of Structural Congenital Anomalies

Abstract

Objective —

To assess the impact of prenatal screening on the birth prevalence of three categories of structural congenital anomaly: abdominal wall defects (omphalocele and gastroschisis), renal agenesis/dysgenesis, and limb reduction defects.

Setting —

Glasgow, Scotland, United Kingdom.

Methods —

Data on the selected defects were obtained retrospectively from the population based Glasgow Register of Congenital Anomalies for the period 1980–91 inclusive. The register records all clinical or laboratory diagnoses of congenital anomaly in live births, stillbirths, and induced abortions occurring in women resident within the boundaries of the Greater Glasgow Health Board. The secular trends in the proportions of the defects diagnosed prenatally and terminated after screening, and in their prevalence at birth and during pregnancy, were examined. A total of 154845 births were surveyed: 309 cases were identified in the selected anomaly categories.

Results —

83 cases of omphalocele/gastroschisis (5·4/10000 births), 92 cases of renal agenesis/dysgenesis (5·9/10000 births), and 134 cases of limb reduction defects (8·7/10000 births) were found. Marked increases occurred over the study period in the proportions of cases diagnosed prenatally but not in the proportions terminated. The greatest difference between the prevalence at birth and during pregnancy was found for omphalocele. There were no significant secular trends in the prevalence of the selected defects.

Conclusions —

Prenatal screening has made a limited epidemiological impact on the prevalence of these defects. It has been moderately (but inconsistently) effective in the avoidance of births of infants with omphalocele/gastroschisis and renal agenesis/dysgenesis but not of limb reduction defects. Future efforts should be directed towards improving the technical aspects of the ultrasonographic detection of fetal abnormalities and exploring in detail, locally, the reasons for the varying pattern of decision making about termination of pregnancy among prospective parents.

Keywords

prenatal diagnosis birth defects epidemiology

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