[Determination of birth term by early ultrasonic examination--wrong, wrong and wrong again?]

The article is a critical review of principal weaknesses in the current use of ultrasonography for determination of gestational age and discusses the fact that the method in its practical use disregards any biological variation in biparietal diameter. It is concluded that second trimester determination of gestational age by ultrasonography has an accuracy no greater than +/- 1.5 weeks. This is comparable to the accuracy of the clinical assessment of maturation in the newborn baby. Ultrasonography as the main indicator of gestational age should be used only when the pregnant woman's own menstrual history is obviously incorrect.