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The relation between long-term temporal trends in stillbirth and neonatal death rates and the congenital malformation frequencies in such deaths were analysed, using data from hospital-based European, USA, and Canadian reports published from 1950. In the last 50 years the overall perinatal mortality rate has fairly steadily improved, decreasing by 65-80%. This was accomplished by the control of some serious problems of early life. However, lingering disorders form an ever larger proportion of the causes of perinatal mortality. Among the prominent of these are congenital malformations, accounting for nearly 30% of perinatal deaths at present. However, this figure conceals important differences between stillbirths and early neonatal deaths. For example, although stillbirth and early neonatal mortality rates have decreased to similar extents during these years, congenital malformations, which were almost equally frequent causes of death in both of them at the beginning of this period, are now about twice as common in early neonatal (one week) deaths as in stillbirths. Other differences between them are in birthweight-related malformation frequencies and in characteristic arrays of malformations. The significance of these patterns and of some geographical variations, and the likelihood of continuing improvement in the stillbirth and early neonatal mortality rates are discussed.

A retrospective study was made of sporadic congenital malformations in newborn mice of nine inbred strains maintained in this laboratory. Young of seven of the strains had externally observable anomalies. In four the frequency was 0.1-0.5% and the defects formed no obvious pattern. In another i t was about 4% and consisted mostly of preaxial polydactyly of the forefoot.In the remaining two the frequency was greater and some of the malformations appeared to constitute particular syndromes. In the C57BL/6JKt strain the overall frequency of malformed offspring was 10.1% and the abnormalities included eye defects, polydactyly, and otocephaly. Those of the eye (microphthalmia and anophthalmia) were commonest and affected females and right eyes much more often than males and left ones. In the A/JKt strain the total frequency of malformed offspring was 10.4% and the abnormalities included cleft lip with or without cleft palate, open eyelid, and polydactyly. Cleft lip was commonest and did not show a sex or side preference.The use of inbred strains to investigate the etiology of sporadic congenital malformations of probable multifactorial origin is to be encouraged.