Prolonged pregnancy

INCIDENCE The standard international definition of prolonged pregnancy accepted by both the WHO and FIG0 is 42 completed weeks or mire (294 days o r no re).’.^ Using this definition, between 4% and 14% will reach this gestation. the average being 100/o.6~.’ It is recognised that women who attend kite for antenatal care may be of uncertain gestation and these inay be over-represented in populations of prolonged. pregnancies. Dating by the last menstrual period alone has a tendency to overestimate the gestational age,8 Gardosi et al. have argued that most pregnancies induced f o r post-term are not in fact prolonged when assessed by ultrasound clates. Using early ultrasound alone to calculate the rate of prolonged pregnancy in women who laboured spontaneously significantly reduced the prolonged rate from 9.5% to 1 .5%.O Meta-analysis has demonstrated that routine use of early ultrasound to calculate gestational age reduces the incidence o f prolonged pregnancy.’" It is therefore apparent that accurate calculation of the estimated date of confinement using ultrasound will have a significant effect in reducing the incidence of prolonged pregnancy.