The central primary follicles develop in the fetus about 60 days into gestation. At between 70 to 90 days the two lateral primaries complete the trio group. After 95 days the secondary follicles begin to develop, the first ones are more apt to be branched and can produce up to eight wool fibers from one follicle. After about 120 days the secondaries are more apt to be an unbranched-type, thus producing only one fiber. All of the primary follicles are formed and growing fibers by the time the lamb is born. While most of the secondaries are developed before birth, they may not mature or produce fiber until after birth. Normally all follicles are producing fibers by a month after birth.