Chromosomal mosaicisms in prenatal diagnosis: correlation with first trimester screening and clinical outcome

To investigate the outcome of pregnancy after detection of chromosomal mosaicism and to determine the correlation between human chorionic gonadotropin (free β-HCG) and pregnancy-associated plasma protein-A (PAPP-A) levels from first-trimester-screening with pregnancy outcome.

In a single-center, retrospective survey of the results of prenatal diagnostics performed between January 2000 and March 2011, we identified a total of 40 pregnancies with chromosomal mosaicism. Clinical characteristics and results of first-trimester screening, as well as the outcome of these cases, are described.

Out of 40 cases, 21 were defined as confined placental mosaicism, 10 classified as true mosaicism and nine were not classifiable cases. Nuchal translucency (NT) was ≥2.5 mm in 8/30 cases with respective measurements. PAPP-A levels were ≤0.4 MoM in 9/26 cases, with respective measurements, two of them being newborns with growth restriction. Remarkably, in pregnancies of all four children born with severe growth retardation, <3rd percentile PAPP-A levels were below 0.52 MoM.

Our observations show mosaic pregnancy outcomes to be very heterogeneous. Nevertheless, a combination of low PAPP-A and interpretation of chromosomal mosaicism might identify pregnancies at particular risk for fetal growth restriction.