It is also unclear whether females heterozygous for the pathogenic c.[833C; –] chromosomes may have had a more favorable pregnancy outcome (reduced bleeding potential)—as proposed in cases of thrombophilia [Gopel et al., 2001; Lindqvist et al., 1998]—under the as yet unproven assumption that heterozygotes for CBS deficiency are in general more prone to thromboembolism [Mudd et al., 1981; Swift and Morrell, 1982]. Here, CBS is linked to Rare hereditary thrombophilia.