Trend of Prenatal Invasive Testing and Down’s Syndrome Screening in a Tertiary Referral Centre in Hong Kong

Abstract

Objectives: To determine (1) the trend of amniocentesis and chorionic villus sampling (CVS), and (2) the number of women aged 35 years or more who underwent Down’s syndrome screening from 1997 to 2005.
Methods: A retrospective review from the clinical database of the Prenatal Diagnosis and Counselling Department was performed. All the data were entered by nurse specialists working in the department. The number and indications of amniocentesis and CVS performed from 1997 to 2005 were retrieved. In addition, the number of such women who underwent Down’s syndrome screening tests was also retrieved.
Results: From 1997 to 2005, the total number of referrals increased from 1680 to 2010, the number of amniocentesis undertaken decreased from 708 (42%) to 390 (19%). Although chromosome study remained as the main indication for amniocentesis (88% to 96%), the numbers performed for that purpose decreased by almost half. In addition, the numbers performed to test for genetic diseases decreased markedly from 38 (6%) to 8 (2%). From 1997 to 2002, the number of CVS procedures decreased from 84 (5%) to 33 (2%), with a decrease in numbers undertaken for chromosome study from 46 to 5. Later, there was an increase in the number of CVS chromosome studies from 8 in 2004 to 22 in 2005. The proportion of women aged 35 years or more who underwent a Down’s syndrome screening test increased from 31% to 65%, while the proportion who underwent an invasive test (amniocentesis or CVS) decreased from 76% in 1997 to 40% in 2005. In 2000, 38% of women aged 35 years or more underwent a second-trimester Down’s syndrome screening test. After the introduction of nuchal translucency scanning in 2001, 41% of women underwent an integrated screening test in 2002, while the proportion who underwent second-trimester Down’s syndrome screening decreased to 11%. With the introduction of first-trimester serum markers for Down’s syndrome in mid-2005, 11% and 1% of women underwent first-trimester combined screening tests and fully integrated screening tests, respectively. Compared to 2004, the proportion of women who underwent the integrated test for Down’s syndrome decreased by 10% and the total proportion of those who underwent such screening increased by 3%.
Conclusion: From 1997 to 2005, the proportion of women aged 35 years or more who underwent a Down’s syndrome screening test increased from about one-third to two-thirds while the proportion who underwent invasive testing decreased by about one half.