From February 2006 to March 2008, 42 pregnant women homozygous for the 677CT-methylenetetrahydrofolate reductase (MTHFR) allele were recruited in our obstetrics service for pregnancy at risk. All had antithrombotic prophylaxis with low-dose aspirin and/or low-molecular-weight heparin, supplemented with folic acid. In all, 2 women lost the fetus and 4 were lost to follow-up before delivery. A total of 36 women delivered term infants who all underwent transfontanellar ultrasonography within 24 hours of birth. Six (16.6%) had ischemic or hemorrhagic cerebral lesions. No differences were observed in gestational age, birth weight, or umbilical cord pH between the 30 healthy infants and the 6 with cerebral lesions. Neonatal outcomes were negative in spite of maternal folic acid supplementation and antithrombotic prophylaxis during pregnancy. This suggests a relationship between maternal homozygous mutation in the 677CT-MTHFR allele and neonatal cerebral lesions.