A new policy for prenatal screening and diagnosis of Down syndrome for pregnant women with advanced maternal age in a public hospital

Abstract

Objective. Before April 2006, women with singleton pregnancy and advanced maternal age (AMA, 35 years and older) were offered either direct invasive tests or a variety of screening tests for Down syndrome (DS) with routine anomaly scan at 18–20 weeks. After April 2006, to reduce procedure-related fetal loss, invasive test was performed only for positive screening result or the presence of major fetal anomaly on ultrasound. We reviewed our 2-year experience after the policy change.

Methods. Two-year data after policy change were compared to the 1-year historic control before policy change.

Results. A total of 2257 eligible women were counselled in the 2 years after policy change. The uptake of screening was 96.7%. The overall detection rate for DS was 90% (18/20) at a false positive rate of 10.9%. The number of invasive tests performed to diagnose one case of DS was reduced 7-fold from 97 to 13.

Conclusions. The number of direct invasive tests was markedly reduced. With effective DS screening policy, it is possible to do away with direct invasive testing for the majority of women with AMA.

Keywords:

• Down syndrome
• screening
• advanced maternal age

Acknowledgements

The authors would like to thank Dr. M. Tang, Dr. E. Lau and Dr. C.P. Lee (Prenatal Diagnosis and Counselling Unit, Tsan Yuk Hospital) for quality control of our NT measurements and reporting of the various DS screening tests, and the staff of the Prenatal Diagnostic Laboratory, University of Hong Kong for their laboratory work.