[Determination of birth date by early ultrasonography]

Ultrasound examination has become an indispensable tool in antenatal care. In cases with intrauterine growth retardation, post-term pregnancy and when deciding elective delivery, knowledge about gestational age is essential. However, criticism has been raised against its routine use to determine gestational age. Ultrasound is subject to a certain degree of variation, as is determination of gestational age on the basis of the last menstrual period. Variation is less by ultrasound, which therefore reduces the number of "post-term" pregnancies. The consequences of post-term pregnancy are discussed.