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[L. gestare, to carry around]
In mammals, the length of time from conception to birth. The average gestation time is a species-specific trait. In humans, the average length, as calculated from the first day of the last normal menstrual period, is 280 days, with a normal range of 259 days (37 weeks) to 287 days (41 weeks). Infants born prior to the 37th week are considered premature and those born after the 41st week, postmature.
SEE: gestational assessment