Abstract
Intrauterine diagnosis of methylmalonic acidemia (MMA-emia) is possible by examining maternal urine for increased levels of methylmalonic acid (MMA) during the third trimester. The possibility of a false positive diagnosis using this method is suggested by the following report.
A clinically normal woman who had previously produced a daughter with B-12 responsive MMA-emia became pregnant by a second husband. Her urinary excretion of MMA during the 36th week of pregnancy was found to be 43.6 mg per 24 hours, comparable to values reported for women carrying 8-month fetuses with MMA-emia. Thus, she was given B-12, 1 mg IM twice weekly. Her urinary MMA excretion just prior to term delivery was 118.1 mg/24 hours. The serum level was 0.24 mg MMA/ml at 8 months of pregnancy and this value decreased to 0.12 mg/ml after partuition. After delivery MMA excretions in the infant were 0.13 and 0.45 mg per 24 hours on B-12 injections and 3.94 mg/24 hours off B-12; corresponding serum levels were 0.19 mg MMA/ml and 0.35 mg/ml, respectively. The infant is not chemically or clinically homozygous for MMA-emia. The increased maternal excretion of methylmalonic acid near partuition may represent a response to the “stress” of pregnancy. The mother has continued to excrete increased amounts of MMA post partum, and the possibility that she is B-12 deficient is being investigated. These observations document the possibility of an erroneous prenatal diagnosis of MMA-emia in an unaffected fetus.
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Netzloff, M., Frias, J. & Rennert, O. FALSE POSITIVE DIAGNOSIS OF FETAL METHYLMALONIC ACID-EMIA DURING PREGNANCY WITH AN UNAFFECTED FETUS. Pediatr Res 11, 461 (1977). https://doi.org/10.1203/00006450-197704000-00545
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DOI: https://doi.org/10.1203/00006450-197704000-00545