Estimation of the date of onset of pregnancy. Relative accuracy and logical use of different clinical and paraclinical factors

The authors have noted that in daily hospital practice there is often a lack of accuracy in assessing the duration of pregnancies. This makes it more difficult to care for pregnant women and makes certain obstetrical decisions less valid. They review the clinical and paraclinical means that are available to estimate the date when pregnancy started, which is the essential reference point. They show how precise different types of information are and how useful they are for the practitioner. In this report they draw attention particularly to the date of the periods, to the levels of chorionic gonadotrophin and to the ultrasound pictures. They have classified under three headings simple rules to make a sensible use of the information that is available: easy cases where the date of conception is know, average cases where the date of the last periods remains the most reliable indication and difficult cases where ultrasound is useful as long as it is carried out early.