This European collaborative study addresses the question whether a predictive test result for Huntington's disease (HD) has an effect on subsequent reproduction by comparing carriers and non-carriers of the Huntington mutation. A unique characteristic of this study is that this evaluation is done in persons at reproductive age who had a predictive test after the identification of the Huntington gene and who were counselled in one of the participating centres. Data were collected for 180 carriers and 271 non-carriers who received a predictive test result in the period 1993 ± 1998 in Aberdeen, Athens, Cardiff, Leiden, Leuven, Paris or Rome. The mean age of the total study group was 31.5 years and for about half of the group the follow-up interval was 3 years or more, with a maximum of 7 years. The collaborative study clearly revealed an overall impact of the predictive test result on subsequent reproduction: 14% of the carriers had one or more subsequent pregnancies vs 28% of the non-carriers. In the total carrier group a prenatal test was carried out in about two thirds of the pregnancies and one child was born after preimplantation genetic diagnosis; artificial insemination by donor, egg cell donation or adoption were not reported. A more refined analysis was performed in the subgroup with a follow-up interval of at least 3 years and who reported`family planning' as a motive to apply for predictive testing in the pretest period. The complexity of this motive is discussed. In this subgroup with a desire for children in the pretest period the effect of the predictive test result was more pronounced: 69% of the non-carriers had subsequent pregnancies while only 39% of the carriers who mentioned`family planning' as one of the major reasons to apply for predictive testing had a subsequent pregnancy. Of the carriers with one or more subsequent pregnancies the percentage using prenatal diagnosis was slightly higher than the percentage not using it, although there were clear differences from one centre to another. The latter group's decisions may seem more intriguing but may be partially understood based on stage theories of health behaviour. Last, but not least, whatever option is chosen by a couple at increased risk of transmitting the Huntington mutation, it is of the utmost importance that professionals fully respect this decision and support the couple.

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This European study involving seven genetic centres from six countries -Aberdeen, Cardiff (UK), Leiden (Netherlands), Leuven (Belgium), Paris (France), Rome (Italy), Athens (Greece) has gathered information on prenatal testing by direct mutation analysis and exclusion testing for Huntington's disease (HD) from the six European countries during the period 1993 -1998. Data describing the parent belonging to the HD family was collected; this included their sex and age as well as their risk of developing HD. Information about previous pregnancies, the rank of the pregnancy being tested and its outcome was also gathered. In addition the number of previous prenatal tests for HD was recorded. Three hundred and five results were recorded by the participating countries between 1993 and 1998. The largest groups came from the UK (157) and the Netherlands (90). The mean age for the parent from the HD family was 30.8 years. In half of the tests the prospective parent was an asymptomatic gene carrier, 42% remained at risk, and 6% of the prospective parents were already showing clinical features of HD. 65% of tests performed used mutation analysis.

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Objectives-To describe the consequences of the identification of the Huntington's disease (HD) mutation on predictive and prenatal testing. Methods-A retrospective study was performed considering the test applicants, procedures, and results before and after the identification of the mutation. 1032 people at risk for Huntington's disease in The Netherlands were included, of whom 741 applied for the predictive test in the period 1987 to 1997 in Leiden at the Department of Clinical Genetics, and after 1994, also in the other seven clinical genetics departments in The Netherlands. Uptake, sociodemographic variables, and test results, taken before and after the mutation was identified, are described. Results-The uptake of the predictive test in the period studied was 24% and for the prenatal test 2%. No diVerences were noted in numbers and sociodemographic data between the period before and after the mutation was identified. After an initial increase in test applicants, a decrease was seen after 1995. After 1993 a significant increase of 25% at risk test applicants and a significant decrease of prenatal exclusion tests was noticed. Only 7% asked for reassessment by mutation analysis. New problems arose after the identification of the mutation, such as the option of reassessing the risk obtained by linkage analysis, direct mutation testing of 25% at risk persons with a parent who does not wish to know, new choices regarding reproduction, and new uncertainties for carriers of intermediate and reduced penetrance alleles and for their oVspring and relatives. Conclusions-Although predictive testing has become reliable and available for every person at risk since the mutation has been identified, the uptake of predictive and prenatal tests fell short of expectation, no change in sociodemographic variables was seen, and a decrease in number of applicants was noted. Furthermore, new uncertainties, psychological problems, and questions arose. (J Neurol Neurosurg Psychiatry 2000;69:579-583)