Exclusion testing for Huntington's disease in pregnancy with a closely linked DNA marker.

55 couples where one partner was at 50% risk of Huntington's disease (HD) were investigated with a DNA probe closely linked to HD, with a view to exclusion testing in a future pregnancy. In 3 of 9 pregnancies so far, HD was excluded in the absence of recombination. In 3 the risk was raised to around 50%, and in 2 exclusion tests were uninformative. The remaining couple changed their minds about termination of the pregnancy and the test was therefore judged inappropriate.