Marker chromosomes in A series of 10000 prenatal diagnoses. Cytogenetic and follow‐up studies

Abstract

In a series of 10,000 prenatal diagnoses 15 marker chromosomes were detected in our centre. Six of these were familial whilst nine had originated de novo. They were analysed with various staining methods. DA-DAPI staining was positive in nine out of 12 pregnancies. Six pregnancies were continued. Five normal children were born, one ended in intrauterine fetal death of a normal fetus at 37 weeks. Nine pregnancies were terminated, showing six normal fetuses, one familial cat-eye syndrome, one fetus with Down syndrome caused by additional trisomy 21 and one fetus with cystic kidneys resp. It is concluded that it seems safe to continue the pregnancy in cases of familial marker, identical to that of one parent, whilst a de novo DA-DAPI positive marker seems to present a low risk for fetal anomalies.

Chromosomal in situ suppression hybridization of human gonosomes and autosomes and its use in clinical cytogenetics

“…An accessory small chromosome of unknown origin can occasionally be found de novo when prenatal diagnosis is performed (Sachs et al 1987). The origin of such marker chromosomes often cannot be deduced from banding patterns.…”

Small supernumerary marker chromosomes (sSMC) in humans

“…These figures are based on a total of 174 cases from several studies (Nielsen and Rasmussen, 1975;Warburton, 1984;Hook and Cross, 1987;Sachs et al, 1987;Djalali, 1990;Blennow et al, 1994). In most of the familial cases there is no discernibly increased risk for fetal abnormalities if an sSMC is also present in a phenotypically normal parent (Bröndum- Nielsen and Mikkelsen, 1995).…”

Small extra ring chromosome derived from chromosome 10p: clinical report and characterisation by FISH.

“…The incidence of ESACs has been estimated to be 0-14 to 0-72 per 1000 newborns2-5 and 0-65 to 1-5 per 1000 fetuses in prenatal studies.' [6][7][8][9][10] Small extra ring chromosomes constitute ap- Hybridisation was performed in a moist chamber at 37-41°C overnight. The slides were then washed three times for five minutes in 50% formamide, 2 x SSC at 42°C and twice in 2 x SSC at 42°C (the cosmids once for five minutes in 2 x SSC at 72°C).…”