[The impact of prenatal diagnosis on the prevention of chromosomal mental retardation. Chromosomal alterations that can be detected by prenatal diagnosis].
BACKGROUND
Recent advances in cytogenetic analysis techniques, in obstetric procedures and in ultrasonography techniques have made it possible to identify chromosome anomalies that are likely to cause mental retardation before it becomes apparent.


METHODS
Certain groups of pregnant females are clearly indicated for access to a prenatal diagnosis. An advanced childbearing age, a previous child with trisomy and the ultrasound detection of morphological anomalies in the foetus are situations that entail a significantly high risk of a foetal chromosomal anomaly. The identification of other risk factors, such as biochemical markers in maternal serum and ultrasound markers, have made it possible to select pregnant females with a higher risk for the most common chromosome anomalies, which include trisomies 21, 18 and 13, in screening programmes that can be applied to all pregnant women. Carriers of a balanced chromosome rearrangement have a clear risk of bearing offspring with a genetic imbalance, which can occasion congenital malformations and/or mental retardation, with specific problems for each type of structural anomaly. An important percentage of the chromosome anomalies that are unexpectedly detected in prenatal diagnosis offer difficulties when it comes to establishing the correlation between the karyotype and the phenotype and forecasting possible mental retardation if the pregnancy reaches full term.


CONCLUSIONS
The number and variety of chromosome anomalies that can be detected prenatally shows the potential of prenatal diagnosis in the prevention of mental retardation due to chromosomal causes.
Soler-Casas
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A
Hospital Clínic de Barcelona, Mejía Lequerica, s/n. E-08028 Barcelona. asoler@clinic.ub. es
Sánchez-Díaz
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A
Morales-Peydró
C
C
D025063:Chromosome Disorders / Q000150:complications / Q000175:diagnosis* / Q000517:prevention & control*; D005260:Female; D006801:Humans; D008607:Intellectual Disability / Q000235:genetics* / Q000517:prevention & control*; D011247:Pregnancy; D011296:Prenatal Diagnosis