Maternal methylmalonic acid concentration: a sensitive marker for neural tube defects

OBJECTIVE: Decreased levels of both folate and viiamin B12 in maternal blood have been implicated in the pathogenesis of neural tube defects (XTD). Our aim was to studv maternal blood folate, red blood cell folate and vitamin B12 levels in addition to amniotic iluid and maternal urine concentrations of methylmalonic acid (MMA) in NTD affected pregnancies as well as in normal control pregnancies. STUDY DESIGN: Blood, urine and amniotic fluid specimens were all collected between 14 and 24 weeks gestation. Control specimens were obtained from women attending routine antenatal clinics. RESULTS: NTD Normal MMA Mean ± S.D.(Range) Mean ± S.D. (Range) a p value Maternal urine 22.06 ±12.58 29 2.47 ±1.12 11 1.0001 (nmol/molereal) (3.15-52.18) (ü.M.26) Amniotic fluid 1.3 ±0.85 3H 0.98 ±0.41 22 0.0463 (nmol/I.) (0.23-1.31) (0.57-2.37) There was no significant difference between normal and NTD pregnancies for serum folate, red blood cell folate and B12 levels. CONCLUSION: Urine and amniotie fluid MMA appear to be verv sensitive markers for a subset of women who mav be inelaholicallv piedisposed to having oilspring with NTD. The\ mav thi'refore represent those women who benefit most from folate and vitamin R12 supplementation in reducing their risk of NTD. Because of the eomplementarv metabolic roles of Colic acid and cobalamin (viiamin B12) it would appeal leasonable to advocate implementation or foitirkalion with both \itamin B12 and folate to reduce NTD risk.