Mutations in several genes, including SERPRINF1 and COL1A1, have been associated with the development of osteogenesis imperfecta (OI). Here, we reported the co-occurrence of a rare heterozygous variant (c.167C>G p.Ala56Gly) in SERPRINF1 and a novel heterozygous mutation (c.1634G>A p.Gly545Asp) in COL1A1 in a foetus with a severe form of OI. Bioinformatics modelling revealed that the effect of the mutation on SPERINF1 is neutral. In contrast, the mutation in COL1A1 is deleterious. It is predicted to cause distortion of the α (1) chain of the type I collagen and results in structural instability of the protein. Therefore, a novel dominant variant of COL1A1 likely underlies the severe foetal pathology observed, although we do not exclude the possibility that the heterozygous mutations in SERPINF and COL1A1 may interact and co-ordinately cause pathogenesis. This novel COL1A1 mutation is recommended to be included in the diagnostic panels for OI.