Maternal phenylketonuria: newborn outcomes in women treated and not treated before pregnancy Maternal phenylketonuria

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Karolina Łagowska
Joanna Pieczyńska


phenyloketonuria, PKU, maternal, nutrition, diet,


The aim of this study was to determine the relationship between the low-phenylalanine diet and perinatal parameters in children of women with phenylketonuria. An attempt was also made to determine whether starting the diet only after the beginning of pregnancy increases the risk of maternal phenylketonuria syndrome in children. Forty-five women from Poland, who were diagnosed with phenylketonuria PKU were recruited. Each subject completed a two-part medical questionnaire. The questions in the first part concerned pregnancy. Part two of the questionnaire referred to the neonates and asked for perinatal parameters. 13% of the surveyed women did not use a low-phenylalanine diet in the period prior to conception, and thus reported that they did not achieve metabolic control of phenylketonuria. The remaining 87% of respondents following this diet during the period prior to conception. Women using the low-phenylalanine diet in the period prior to conception gave birth to children with significantly higher birth weights and larger head circumferences. In all the women, regardless of whether they used the low phenylalanine diet prior to pregnancy or not, the average blood phenylalanine concentration decreased over subsequent trimesters. Birth defects were significantly more common in the case of women who did employ the low-phenylalanine diet in the period prior to conception.  We underline that the treatment of pregnant women with phenylketonuria is of great importance to prevent neonatal sequelae. We strongly recommend starting treatment prior to conception, as the deleterious effect of not using the low-phenylalanine diet in period prior to conception is very clear.


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