In the hope of reducing perinatal risks associated with retardation of intrauterine growth a previously described two stage ultrasound screening schedule was evaluated by a controlled trial in 877 women with low risk single pregnancies. The two stages of ultrasound examination were an assessment of gestational age during early pregnancy followed by measurement of length from crown to rump and area of trunk at between 34 and 36 weeks' gestation. The product of crown to rump length and trunk area was calculated.The sensitivity of this schedule in identifying in advance 94% of babies who were small for dates at birth, with 90% specificity, and the speed and simplicity of measurement confirmed the accuracy and feasibility of two stage ultrasonography as a screening procedure. The controlled trial did not, however, show any benefit from its routine application in these low risk pregnancies.

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Adapting Sir Dugald Baird's concept of primary obstetric causes of perinatal mortality, a revised clinico-pathological classification has been evolved to take account of new knowledge and developments, and to direct attention to potentially avoidable deaths and to where intensified efforts and investigation are needed. Categories highlighting the importance of intrauterine growth retardation, unexplained intrauterine death and spontaneous premature labour have been introduced, intrapartum hypoxia is separated from birth trauma, and infection again has its own category. Regular perinatal audit at one obstetric hospital, since 1979, has shown that the new system provides a workable and useful means for classifying not only perinatal deaths, but also late abortions, late neonatal deaths and perinatally related infant deaths. The rate of total perinatally related wastage, defined in this way, was almost twice that for perinatal mortality (22-8 compared with 11.9 per 1000 births). The former is advocated as a more realistic index for the audit of perinatal care. The revised and extended system is put forward as a contribution to the current debate on classifying and reporting such wastage, in the hope that it may be tested as a model for regional as well as hospital surveys.Perinatal mortality should be classified in several ways-epidemiological, by time in relation to birth (stillbirths and first week neonatal deaths; or antepartum, intrapartum and postpartum), obstetric, neonatal and pathological. Each has

Summary A new method of estimating fetal weight from the circumference of the fetal trunk, measured by ultrasound, is described. Comparison of weights estimated in this way with the actual birth weights of 50 fetuses, delivered not more than 48 hours later, shows a mean error in prediction of only 75 g, and in 94 per cent the error was less than 145 g. With such accuracy, the method is of clinical value, particularly in anticipating difficult delivery and in monitoring growth of the fetus at risk.