Congenital malformations associated with anencephaly in the Fylde peninsula of Lancashire.

The necropsy reports of 174 cases of anencephaly, born in the Fylde peninsula of Lancashire between 1957 and 1980, have been analysed for the presence of other malformations. The results were compared with a similar previous series from Bristol, though the Bristol study differed both in time (1948 to 1975) and in the fact that it was hospital based and, unlike the present study, did not achieve near complete ascertainment. Of the Lancashire anencephalics, 24% had other malformations, a significantly lower rate than in the Bristol series. There was a much higher rate of renal and urinary tract defects in the Bristol series, and a higher rate of cardiovascular defects in the Lancashire series. The distribution of associated malformations differed in the two areas, possibly representing different patterns of aetiological heterogeneity. The iniencephaly rate was so much lower in Lancashire as to suggest an artefact, perhaps owing to the lack of a precise definition of the condition.