Increased nuchal translucency and decreased fetomaternal transfusion after chorionic villus sampling

To investigate the relationship between nuchal translucency (NT) and fetomaternal transfusion (FMT) after chorionic villus sampling (CVS).

The level of FMT was determined in 272 viable, singleton pregnancies in which 10-14-week ultrasound scanning, NT measurement and CVS for fetal karyotyping had been performed. The pre-CVS NT was measured transvaginally, and the women were divided into two groups, i.e. those with NT < 2.5 mm (Group 1) or >or= 2.5 mm (Group 2). The level of FMT was determined via the maternal serum alpha-fetoprotein levels before and after CVS. FMT was analyzed in relation to the pre-CVS NT.

Of the 272 pregnancies, 213 were in Group 1 and 59 in Group 2. The mean levels of FMT after CVS were 23.3 +/- 12.2 and 5.4 +/- 2.9 micro L in Groups 1 and 2, respectively (P < 0.01). An FMT > 100 micro L was found in 19 cases in Group 1, whereas the maximum in Group 2 was 67.2 micro L. Aneuploidies were diagnosed in 17 cases, 15 (88.2%) of them in Group 2. When the pregnancies with adverse outcome were excluded from the two groups, a higher level of FMT was observed in Subgroup 1 than in Subgroup 2 (P < 0.01).

The mean level of FMT after CVS was significantly lower in pregnancies with an increased pre-CVS NT, a relationship observed in euploid pregnancies also. An increased pre-CVS NT seems to be inversely correlated with the FMT increase after CVS. Further studies are planned to investigate the background to this phenomenon.