Screening for chromosomal abnormalities by first trimester combined screening and noninvasive prenatal testing

Area of Science:

• Prenatal diagnostics
• Genetics
• Maternal-fetal medicine

Background:

• First Trimester Screening (FTS) and Noninvasive Prenatal Testing (NIPT) are key methods for detecting fetal aneuploidies.
• Evaluating combined screening strategies is crucial for improving diagnostic accuracy and patient outcomes.
• A two-step policy integrates FTS and NIPT to leverage the strengths of both screening methods.

Purpose of the Study:

• To assess the effectiveness of combined FTS and NIPT in screening for fetal aneuploidies.
• To compare the performance of different screening policies, including standalone FTS, standalone NIPT, and a two-step approach.
• To determine the optimal screening strategy for maximizing aneuploidy detection rates.

Main Methods:

• Retrospective analysis of 21,052 pregnancies undergoing FTS.
• Calculation of combined risk for trisomy 21, 18, and 13.
• Simulation of screening policies: NIPT, FTS, and a two-step FTS-NIPT approach with varying risk cut-offs.

Main Results:

• FTS detected 81-91% of aneuploidies, while NIPT detected 88%.
• The two-step FTS-NIPT strategy achieved detection rates of 93-94% for all aneuploidies.
• A total of 127 trisomy 21, 34 trisomy 18, and 13 trisomy 13 cases were identified.

Conclusions:

• A two-step screening policy combining FTS for all patients and NIPT for the intermediate-risk group yields the highest detection rate for fetal aneuploidies.
• This integrated approach enhances the accuracy of prenatal screening for chromosomal abnormalities.
• The findings support the implementation of a two-step FTS-NIPT strategy for improved aneuploidy detection.