[Prenatal diagnosis of cystic fibrosis]

A review is presented of prenatal diagnosis of cystic fibrosis (CF). Two approaches are presently available: DNA-probing in chorionic villi (8th-10th week of gestation) and determination of microvillar enzymes in amniotic fluid (17th or 18th week of gestation). DNA-probing makes use of linked markers (restriction fragment length polymorphisms). This means that prenatal diagnosis is only possible when DNA of an earlier affected sib is available. Moreover the parents have to be informative with respect to the DNA-markers. This is the case in the majority of families, but not in all of them. Also the possibility of recombination has to be taken into account. For that reason families should preferably be referred before pregnancy. In the majority of cases presence or absence of CF in the fetus can be determined with high probability. A hundred percent certainty however is not possible with present techniques. Determination of microvillar enzymes in amniotic fluid is based on the fact that the concentration of these enzymes in general is lower in CF fetusses than in normal ones. There are however overlapping values. So, also with this technique, a hundred percent certainty is impossible. This type of prenatal diagnosis is especially suitable in families in which DNA-probing is impossible or gives insufficient discrimination between affected and unaffected fetusses. Looking for a meconium accumulation by means of ultrasound can support diagnosis.