Congenital heart disease in maternal phenylketonuria: Effects of blood phenylalanine and nutrient intake

The incidence of congenital heart disease was found to be 7.5% from 414 offspring born to women with phenylketonuria in the National Collaborative Study for Maternal Phenylketonuria (MPKU). Nutrient intake was studied in a subset of 22 offspring with congenital heart disease. The infants with congenital heart disease were divided into two groups, those whose mothers consumed greater than 50% of the recommended dietary allowance (RDA) for protein and those who had consumed less than 50% of the RDA for protein during the pregnancy. The subjects were further categorized based on the blood phenylalanine of the mother of less than or greater than 10 mg/dl during the first eight weeks of gestation. All of the women who produced offspring with congenital heart disease had blood phenylalanine concentrations greater than 10 mg/dl during the first eight weeks of gestation. A Fisher's Exact test showed that there were a significantly greater number of offspring born to women who had low protein intake (p > 0.0013). Stepwise analysis indicated first trimester variables that discriminate infants with congenital heart disease. These variables included dietary intake of protein, blood phenylalanine from weeks 4-8 of gestation, dietary fat intake, the initial blood phenylalanine concentration, and intake of vitamin B₁₂. An Odds ratio showed that intake of vitamin B₁₂ was a predictor of congenital heart disease among treated women with PKU.