How long should a fetus be at 13 weeks?

At 13 weeks of gestation, a fetus typically measures about 2.9 inches (7.4 centimeters) in length from crown to rump. This is equivalent to approximately the size of a medium-sized lime. By this stage, many of the major organs and systems are developing, and the fetus is beginning to move, although these movements may not yet be felt by the mother.