[Determination of gestational age using crown-rump length and the biparietal diameter in the 1st half of pregnancy--comparison of 2 methods].

In the first half of pregnancy ultrasound investigations was made on women with known gestational age by regular menstruation or conception. In 221 cases of single pregnancies fetal crownrump length was measured. Biparietal cephalometry was performed in 198 single fetuses. All examinations were done with a Kranzbühler Linearscanner using an ADR 3.5 MHZ transducer. Growth curves and the velocity of growth from biparietal diameter and from crown-rump length were determined and compared. The accuracy of the estimation of gestational age was observed to be +/- 10 days (2 SD) with both methods. A difference in accuracy could not be found. Even if the first half of pregnancy was separated in an early and a late part there wasn't any improvement of accuracy.