Infertility

The object of this paper is to discuss the routine use of ultrasound in estimating the date of delivery and to demonstrate an approach which has both sound epidemiological and statistical bases. CESDI (Confidential Enquiry into Still Births and Deaths in Infancy) criteria for determining gestation, based on menstrual dates and cycle length superseded by an ultrasound scan different by more than ten days, are difficult to apply.