First trimester screening for aneuploidies in successive pregnancies: correlations between markers

Screening for chromosomal abnormalities in the first trimester of pregnancy is based on maternal age, nuchal translucency (NT), and biochemical markers (pregnancy-associated plasma protein-A and free beta human chorionic gonadotrophin). We have assessed the influence of screenings and outcomes in previous pregnancies on screenings in subsequent pregnancies.

Retrospective study of the correlation between the variables of first trimester combined screening for chromosome abnormalities in patients with subsequent pregnancies. Excluded were gestations with fetal aneuploidies.

Between July 1999 and December 2009, there were 2291 women with more than 1 euploid pregnancy screened in the first trimester in our hospital. There was a moderate correlation for pregnancy-associated plasma protein-A (ρ = 0.530, p <0.001) and free beta human chorionic gonadotrophin (ρ = 0.439, p <0.001) between the first and second pregnancy. The trend continued in successive pregnancies. NT showed no correlations of clinical importance. With an overall false positive (FP) rate of 2.1% for the combined screening, the probability of having a recurrent FP in the second pregnancy was 4.3% (not significant).

There are significant correlations between biochemical markers but not NT in successive pregnancies, leading to increased risk of recurrence of FP results. However, such increase is not statistically significant if the overall FP rate is very low.