THE IMPACT OF PRENATAL-DIAGNOSIS ON THE INCIDENCE OF HEMOPHILIA IN SWEDEN

A demographic survey was made of all children (n = 137) born with seve re or moderate haemophilia in Sweden during the period 1970-92. In add ition, all prenatal diagnoses (n=86) performing during the period were evaluated. The annual incidence of severe and moderate haemophilia, h aving remained constant for decades, increased from 0.78/10,000 males in the 1970s to 1.34 in the 1980s, levelling off at 1.31 in the 1990s. Although prenatal diagnosis did not affect the incidence of haemophil ia in the 1970s and 1980s, it did so in the 1990s, because the inciden ce would have been 40% higher (1.83) had not prenatal diagnosis been a vailable and 16 affected fetuses been aborted. The average proportion of sporadic cases, 62%, remained almost unchanged during the study per iod, suggesting mutation rates to be constant. There were fewer childr en in families with known haemophilia than in sporadic families, but n o evidence was found to suggest that the frequency of female offspring (i.e. potential carriers) born in haemophilia families had increased since the option of prenatal diagnosis was introduced.