Hyperhomocysteinemia ‐ A risk factor for abruptio placentae

Recurrent early spontaneous abortion has been linked to hyperhomocysteinaemia (Steegers-Theunissen et al 1992;Wouters et al 1993).Homocysteine is derived from the essential amino acid methionine.It can be remethylated to methionine by betaine-homocysteine methyltransferase or by methionine synthase, which requires 5-methyltetrahydrofolate as the methyl donor and vitamin B 12 as cofactor.Excess homocysteine can be irreversibly trans-sulphurated via cystathionine into cysteine, in which the first reaction is catalysed by cystathionine β -synthase which is dependent on the cofactor pyridoxal 5-phosphate (PLP, a form of vitamin B 6 ).Heterozygotes for cysta-thionine β -synthase deficiency have been shown to have hyperhomocysteinemia and have been estimated to occur with a frequency between 1:100 and 1:200 in the normal popu-lation (Mudd et al 1989).However, Steegers-Theunissen et al (1992) reported normal cystathionine βsynthase activity (control range 1.8-18.9nmol/hper mg protein in cultivated fibroblasts) in patients with hyperhomocysteinemia and a history of early spontaneous abortion, so elevated levels of serum homocysteine do not necessarily imply the presence of a defective cystathionine β -synthase gene.We undertook in this study to investigate the relationship between total homocysteine levels and cystathionine β -synthase activity in patients with abruptio placentae in order to try to resolve that discrepancy.