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PEDIATRICS Vol. 112 No. 6 December 2003, pp. 1548-1552

SUPPLEMENT ARTICLE

Pregnancy Experiences in the Woman With Mild Hyperphenylalaninemia

Harvey L. Levy, MD*, Susan E. Waisbren, PhD{ddagger},§, Flemming Güttler, MD, PhD||, William B. Hanley, MD, Reuben Matalon, MD, PhD#, Bobbye Rouse, MD#, Friedrich K. Trefz, MD**, Felix de la Cruz, MD, MPH{ddagger}{ddagger}, Colleen G. Azen, MS§§ and Richard Koch, MD§§

* Division of Genetics, Children’s Hospital Boston, Boston, Massachusetts
{ddagger} Department of Pediatrics, Harvard Medical School, Boston, Massachusetts
§ Department of Psychiatry, Harvard Medical School, Boston, Massachusetts
|| John F. Kennedy Institute, Glostrup, Denmark
Hospital for Sick Children, Toronto, Ontario, Canada
# University of Texas Medical Branch, Galveston, Texas
** Children’s Hospital of Reutlingen, Reutlingen, Germany
{ddagger}{ddagger} National Institute of Child Health and Human Development, Bethesda, Maryland
§§ Children’s Hospital Los Angeles, Los Angeles, California

Objective. A major issue in maternal phenylketonuria (MPKU) has been whether maternal non-PKU mild hyperphenylalaninemia (MHP) is teratogenic. Such untreated pregnancies and their outcomes are presented on this report.

Methods. Enrolled pregnancies in which the untreated prepregnancy assigned phenylalanine level (APL) was no more than 600 µmol/L were included in the Maternal PKU Collaborative Study and were followed according to protocol.

Results. Forty-eight enrolled women with non-PKU MHP had mean APL 408 ± 114 µmol/L. They had a total of 58 pregnancies that resulted in live births. Fifty were untreated. Maternal phenylalanine (Phe) levels in the untreated pregnancies decreased during pregnancy for average Phe exposure of 270 ± 84 µmol/L, virtually identical to the level of 269 ± 136 µmol/L in the 8 treated pregnancies. Birth measurements in the 50 offspring from untreated pregnancies were within normal limits with z scores of –0.25 for weight, 0.28 for length, and –0.63 for head circumference, although birth head circumference was negatively correlated with maternal APL (r = –0.30). Only 1 offspring had congenital heart disease. Offspring IQ was 102 ± 15 compared with 96 ± 14 in the mothers with untreated pregnancies and with 109 ± 21 in control offspring.

Conclusion. Maternal non-PKU MHP no more than 600 µmol/L does not require dietary therapy. The naturally lower Phe level during pregnancy seems to protect against teratogenesis.

Key Words: maternal phenylalanine • genotype • offspring • birth weight • birth length • birth head circumference • IQ

Abbreviations: MPKU, maternal phenylketonuria • Phe, phenylalanine • CHD, congenital heart disease • MHP, mild hyperphenylalaninemia • HPA, hyperphenylalaninemia • MPKUCS, Maternal PKU Collaborative Study • APL, assigned blood phenylalanine level • PAH, phenylalanine hydroxylase • SD, standard deviation