Gestational age assessment. I. analysis of individual clinical observations.

Accurate assessment of the estimated date of confinement is a cornerstone of obstetric care. Traditionally this date has been predicted from historical and clinical examinations; however, there have been few studies of the accuracy of such predictions. Multiple estimators of gestational age were examined in 418 patients who were delivered of infants weighting larger than or equal to 3,000 gm, following spontaneous onset of labor. Mean intervals from an event to delivery were calculated for last menstrual period (284.2 days), quickening (156.3 days), first audible fetal heart tones (136.2 days), uterine fundus at the umbilicus (140.8 days), and measurements of the fundal height. The variability in each of these estimators was examined and compared. The last menstrual period, if known with certainty, is the most accurate estimator, followed by the uterus at the umbilicus, first heard fetal heart tones, fundal height, and quickening.