Pregnancy—estimated duration

Guide for use:

The duration of a pregnancy on the day of the first antenatal visit has the same value as the best estimate of gestational age for the fetus or baby.
There may be one or more revisions of pregnancy duration after the first antenatal visit if a better estimate of gestational age of the fetus or baby becomes available. Revised estimates are not usually applied retrospectively in health records. The best estimate of pregnancy duration is used to record the gestation at later antenatal visits and to assign gestational age to the baby recorded at the time of birth.
If gestational age has been revised, a similar revision will need to be applied to earlier recorded estimates of pregnancy duration. Alternatively the pregnancy duration on a specified day can be calculated from the gestational age on the day of the baby at birth.