Impact of routine fetal ultrasonographic screening on the prevalence of Down syndrome in non aged mothers.

Abstract

In many countries the introduction of screening programs based on maternal serum has reduced the number of Down syndrome. In France routine maternal serum screening was not available whereas ultrasound scanning during pregnancy is routine practice in private offices and in hospitals using high-resolution real-time scanners and there are no legal upper limits on gestational age at termination of pregnancy for fetal abnormality. The objective of this study was to determine the impact of routine fetal ultrasonographic screening on birth prevalence of Down syndrome in non aged mothers. Total prevalence of Down syndrome during 1989 to 1996 was stable 1.43 per 1,000 with no upward or downward trend. The total number of liveborn Down syndrome during this period was higher than previously due to a changing pattern of risk in relation to maternal age. All women who delivered an infant with Down syndrome had had routine ultrasonography, including 88% in the second trimester. Out of the 154 Down syndrome fetuses examined, 38 had been found to have an anomaly. This low sensitivity (24.7%) is not the result of the quality of the ultrasound equipment. It may be explained by the inadequate routine, first level ultrasonographic examination. This study demonstrated that other screening methods than routine fetal ultrasonographic examination are needed in our region.