The North American Maternal Phenylketonuria Collaborative Study, developmental assessment of the offspring: preliminary report.

Preliminary results of 2-year Bayley and 4-year McCarthy test scores are presented. To date numbers are too small to statistically correlate:- offspring from pregnancies in which diet was started prior to conception, offspring from pregnancies with phenylalanine (Phe) levels of 120-360 mumol/l versus 360-600 mumol/l, influence of home environment, influence of maternal nutrition, language development, behaviour/hyperactivity, Revised Wechsler Intelligence Score, school performance and learning disabilities. Two-year Bayley scores (mental and motor) revealed a median developmental quotient of 113 in 58 offspring from control pregnancies, 104 in 19 offspring from untreated "non-phenylketonuria (PKU) mild hyperphenylalaninaemia" (natural Phe levels < 600 mumol/l) pregnancies, 104 in 32 offspring from pregnancies whose Phe levels decreased on treatment to < 600 mumol/l by 10 weeks gestation and remained in that range for the remainder of the pregnancy, 98 in offspring from 32 pregnancies where permanent control was not achieved until 10-20 weeks and 72 in offspring from 51 pregnancies where control was not attained until after 20 weeks gestation. IQ scores determined by the McCarthy test at age 4-5 years revealed a mean of 112 in 43 offspring of control mothers, 99 in 12 offspring of "non PKU mild hyperphenylalaninaemia" women, 93 in 14 offspring whose mother's Phe levels were continuously under 600 mumol/l by 10 weeks gestation, 88 in 24 offspring from pregnancies in metabolic control by 10-20 weeks and 73 in 28 offspring of pregnancies not in metabolic control until after 20 weeks gestation. These preliminary results suggest that early and adequate dietary treatment during pregnancy in maternal PKU may provide some protection to the fetus for later intellectual development but much more data is required before definitive statements about cognition can be made.