The G985A mutation represents about 90% of all medium-chain acyl-CoA dehydrogenase (MCAD) allele mutations that cause the clinical symptoms of MCAD deficiency. The prevalence of carriers varies between different European populations, with high frequencies in the northwestern part of Europe. To determine the prevalence of MCAD carriers with the G985A mutation in The Netherlands, we collected 6195 Guthrie cards of newborns. Mutation detection was performed with the polymerase chain reaction (PCR), in which a NcoI restriction site was created in the presence of a G985A mutation in the PCR product, followed by NcoI digestion, and gel electrophoresis. We detected a G985A carrier frequency of 1 in 59 (95% CI 1/50-1/73) in The Netherlands. The total prevalence of carriers was estimated to be 1 in 55 (95% CI 1/46- 1/68), based on a relative G985A frequency of 94% in The Netherlands.

SUMMARY Child bearing at an early age and prenatal cytogenetic diagnosis in pregnant women of advanced age, combined with selective abortion, make it possible to avoid the birth of many children with serious chromosomal anomalies. To see how many of such births were still avoidable in Europe, data from 16 regional EUROCAT registers of congenital anomalies in nine EEC countries were analysed. In the period 1979-1982 about 30% of children with unbalanced anomalies of autosomes were born (live-and still-births) to mothers over 35 years of age. This amounts to an estimated 1300 cases yearly in the entire population of the nine countries. The approach shows the possible use of registry data for monitoring effects of avoidance strategies.As women grow older their risk of having children with chromosomal anomalies increases.' This maternal age effect opens the way to reduction of the number of affected children, either by earlier child bearing or by prenatal cytogenetic diagnosis and selective abortion in older pregnant women.

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Investigation of mild, inherited increased serum alkaline phosphatase activity partially combined with Gilbert's syndrome in one family showed, apart from a normal liver fraction, an intestinal iso-

We report here a database listing Mendelian phenotypes described in the Netherlands and/or in populations originating from this country, and describe the results of a quantitative analysis of the database. The database is specifically directed at the presence, frequency and origin of the phenotypes. These are arranged according to their mode of inheritance: autosomal dominant (AD), autosomal recessive (AR) and X-linked. Only those phenotypes which have been reported in accessible sources were included. We entered 1,482 references up to January 1,1991. At least 672 different loci were decribed in the Netherlands at this date: 321 (47.8%) AD, 283 (42.1%) AR and 68 (10.1%) X-linked. Almost 2.5% of all loci in our database have no comparable entry in McKusick [Mendelian Inheritance in Man, ed 9. Baltimore, The Johns Hopkins University Press, 1990] (MIM). There is a significant difference (p < 0.01) according to the division into AD, AR, and X-linked phenotypes between our database and MIM, in which 61.7% of the phenotypes are AD, 31.5% AR and 6.8% X-linked. Dutch prevalence data for 38 monogenic disorders and 24 polymorphic systems are listed.