The rate of invasive testing for trisomy 21 is reduced after implementation of NIPT.

INTRODUCTION

The non-invasive prenatal test (NIPT) was introduced in the North Denmark Region in March 2013. NIPT is offered as an alternative to invasive tests if the combined first trimester risk of trisomy 21 (T21) is ≥ 1:300. The purpose of this study was to investigate the effect of NIPT implementation among high-risk pregnancies in a region with existing first-trimester combined screening for T21. The primary objective was to examine the effect on the invasive testing rate.

METHODS

This was a retrospective observational study including high-risk singleton pregnancies in the North Denmark Region. The women were included in two periods, i.e. before and after the implementation of NIPT, respectively. Group 1 (before NIPT): n = 253 and Group 2 (after NIPT): n = 302.

RESULTS

After NIPT implementation, the invasive testing rate fell from 70% to 48% (p < 0.01), and the number of high-risk women refusing further testing dropped from 26% to 3% (p < 0.01). NIPT successfully detected four cases of T21; however, two out of three sex-chromosomal abnormalities were false positives. No false negative NIPT results were revealed in this study.

CONCLUSIONS

In the North Denmark Region, the implementation of NIPT in high-risk pregnancies significantly reduced the rate of invasive testing. However, the proportion of high-risk women who opted for prenatal tests increased as the majority of women who previously refused further testing now opted for the NIPT.

FUNDING

none.

TRIAL REGISTRATION

The study was approved by the Danish Data Protection Agency (No. 2015-104).