2008 Barcelona - European Society of Human Genetics

Prenental diagnostics
nuchal translucency . Cytogenetic analysis after short-term culture
showed four different abnormal cell lines involving chromosome 18,
and the karyotype was described as:
mos 46,XX,18p+[15]/r(18)[14]/i(18q)[1]/45,XX,-18[3] . Amniocentesis
was subsequently performed . Ultrasound examination showed a
septate translucency as the only abnormal finding. QF-PCR analysis
showed homozygosity for all 18p markers, suggesting a 18p monosomy
. The karyotype obtained was 46,XX,del(18p) in all cells . The pregnancy
was terminated and pathologic studies are being performed at
present. We propose a model to explain the cytogenetic findings. A first
postzygotic error, probably an unequal sister chromatid exchange giving
rise to a cell line with del(18p) and the complementary with 18p+,
may have most likely happened before the first post-zygotic division,
since no normal cells have been detected . Isochromosome(18q) and
ring(18) seem to be secondary to del(18p), and monosomy 18 may
have derived from the ring(18) cell line, given the instability of rings . An
unequal distribution of the different cell lines between the trophoblast
and the inner cell mass, and differences on the viability of each cell
line in different tissues, may explain why the fetal tissues only show the
18p deletion whereas the trophoblast presents the other cell lines .
P03.64
Uptake of prenatal diagnosis after established carrier status of
a balanced structural chromosome abnormality in couples with
recurrent miscarriage
F. Vansenne, J. C. Korevaar, M. T. M. Franssen, N. J. Leschot, F. van der
Veen, P. M. M. Bossuyt, C. A. J. M. de Borgie, M. Goddijn;
Academic Medical Centre, Amsterdam, The Netherlands.
Three to six percent of couples with recurrent miscarriage are carriers
of a structural chromosome abnormality . These carriers are offered
prenatal diagnosis (PND) in subsequent pregnancies . It is unknown
what the effect is of disclosure of the abnormal result of karyotyping in
carrier couples on the uptake of PND in subsequent pregnancies . This
study evaluates the uptake of PND in carrier couples compared with
non-carrier couples .
We collected data of 239 carrier and 389 non-carrier couples presenting
for parental karyotyping after two or more miscarriages < 20 weeks
of gestation in six centers for Clinical Genetics in the Netherlands,
from 1992-2001 . PND procedures in subsequent pregnancies were
recorded for a minimum of 24 months .
Within the carrier couples 150 out of 239 (63%) underwent a PNDprocedure
in at least one subsequent pregnancy compared to 111 out
of 389 non-carrier couples (29%) (p