Does timing of biochemistry in first-trimester aneuploidy risk assessment affect the gestational age at prenatal diagnosis and pregnancy termination?

Overview

OBJECTIVE: To determine the relationship between the timing of chemistry and timing of prenatal diagnosis and pregnancy termination in pregnancies with chromosomal abnormalities. METHOD: Singleton pregnancies with chromosomal abnormalities from 2005 to 2009 were identified. Records were reviewed to identify timing of chemistry, nuchal translucency (NT), prenatal diagnosis and pregnancy termination. Mann-Whitney U and Fisher's exact test were used for statistical analysis. RESULTS: A total of 110 pregnancies were included. Seventy-eight had biochemistry performed at the time of NT and 32 had biochemistry a median of 9 days prior. Aneuploidy risks were similar between the two groups. Although the timing of NT was similar, those having biochemistry before NT had prenatal diagnosis and pregnancy termination at significantly earlier gestational ages. Those with early biochemistry were more likely to have chorionic villus sampling (CVS) (69% vs 37%; p = 0.003) compared to those who had biochemistry at the time of NT. CONCLUSION: There was a strong correlation between the timing of biochemistry and prenatal diagnosis and pregnancy termination.