Diagnosis of pregnancy at term

a) A term fetus has reached a stage of development that will allow the best chance for extra-uterine survival (37 - 41 weeks). Whether a fetus has reached this stage, can be determined by the methods outlined above for ascertaining foetal age and EDD. At term, a fetus usually weighs more than 2500 g. Depending on maternal factors such as obesity and diabetes, amniotic fluid volume, and genetic and racial factors, the baby may be larger or smaller than expected. Therefore, the clinician must rely on objective data to determine fetal maturity

b) Calculation of gestational age (Pregnancy calendar or calculator): normally, human pregnancy lasts 280 days or 40 weeks (9 calendar months or 10 lunar months) from the last normal menstrual period (LNMP). This may also be calculated as 266 days or 38 weeks from the last ovulation in a normal 28-day cycle. The easiest method of determining gestational age is using a pregnancy calendar or calculator.

The estimated date of delivery (EDD) can be determined mathematically using Nägele's rule: subtract 3 months from the month of the LNMP, and add 7 to the first day of the LNMP. Example: With an LNMP of July 14, the EDC is April 21