Maternal phenylketonuria. A study from the United Kingdom.

By November 1994, 39 pregnancies had been completed in phenylketonuric mothers. Dietary control was post-conception in 6 and 2 of these offspring died of congenital heart disease and 1 other needed surgery for coarctation. There were no heart defects in the 34 offspring of the 33 pregnancies following preconception diet controlled by Guthrie assays of maternal phenylalanine three (Phe) weekly. These Phe results were analysed by trimester for the means, the number of days over 300 mumol/l or below 60 mumol/l. Generally good control was achieved suggesting the UK guidelines drawn up by the MRC Working Party are broadly achievable but excessively high and low values occur intermittently in many pregnancies both of which may adversely affect the fetus. Though developmental assessment scores at 1 year were over 100 in all but five, early outcome results suggest that intellectual development may still be impaired at 4 years. Until much more information is available caution is still needed in discussing outcome with phenylketonuria patients who wish to conceive.