Haemophilia A. Thirty-one pregnant women, obligate or probable carriers of haemophilia A, requested prenatal diagnosis if sex determination showed the foetus to be a male. In 11 of the 31 cases the foetuses were females; in two, the genetic variant of the disease rendered prenatal diagnosis impossible; and in two, the mother aborted spontaneously. From the remaining 16 male foetuses, blood samples were obtained in utero in the 17th to 20th week of gestation. Examination of the samples showed that 11 of the foetuses were unaffected and five affected. Haemophilia B. Three carriers of haemophilia B had male foetuses. Examination of foetal blood obtained in utero showed that these three foetuses were affected. Confirmation. All women with an affected foetus requested termination of pregnancy. In one of the cases of abortion, no blood was obtained for confirmative examination. In the remaining cases, the prenatal prediction was confirmed in the abortus or in the child after birth; three women are still pregnant.