Introduction: Haemophilias are X-linked inherited bleeding disorders, due to de novo F8/F9 gene variants in 30-50% of cases. The identification of causative variant in index cases (IC) is crucial for genetic counselling in related women. Over the last 20 years the Emilia-Romagna Regional Haemophilia Registry documented high proportions of sporadic severe haemophilia.
Aim: To clarify if carriers' reproductive choices influence the sporadic/familial ratio of severe haemophilia.
Methods: Genetic counselling and genotyping in 221 relatives of severe IC were retrospectively reviewed, retrieving reproductive choices and pregnancy history of childbearing-age carriers from familial and sporadic pedigrees and according to the IC degree of relationship (mothers, daughters, II/other).
Results: Carriers' identification rates were lower in sporadic women and in other-degree relatives. Among childbearing age women (n = 140), carriers were 37/48 (77%) and 57/92 (62%) of familial and sporadic relatives, respectively. Forty-five/57 sporadic carriers experienced 67 pregnancies, while 21/37 familial carriers had 39 pregnancies (four voluntary terminations), with a significantly higher number of affected sons in the former (40/67 vs. 12/35, P = .025). Prenatal diagnosis was chosen by 40% and 47% of sporadic and familial aware carriers, respectively. Sporadic mothers often avoided further pregnancies (17/38, 45%) after a firstborn affected child, while familial mothers tended to face pregnancies without prenatal approaches (6/10, 60%).
Conclusion: In this cohort sporadic offspring account for more than 70% of severe haemophilia cases. This increasing proportion is likely to reflect the influence in reproductive choices of awareness of carriers' status, particularly in sporadic mothers, and of prenatal diagnosis options.
Keywords: carriers; genetic counselling; molecular diagnosis; pregnancy; prenatal diagnosis; sporadic haemophilia.
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