Foetus is what mammals are when they have not yet been born, and have passed the embryonic stage. A fertilized egg instills itself in the womb it forms an human embryo. After nine weeks of accelerated growth does it enters the foetal stage when it is called as the foetus. In scientific terms foetus refers to your unborn child in the womb. From the start of the ninth week of your pregnancy till your delivery your unborn baby can be referred to as a foetus. In the initial stages the foetus weighs only 8 gm and is typically 1.2 inches from top to toe. The head makes up nearly half of the foetus size. In fact an egg graduates to become a foetus when it has the heart, hands, feet, brain and other organs present though in its nascent stage and is hardly operative.
Foetal development or movements that a mother feels in her second trimester or around 21 weeks indicates that the foetus is growing well and at an expected pace. These small indications by the foetus also stand to be an important milestone in diagnosing the progress of the pregnancy. In the second trimester the foetus is 8 inches in length. As the pregnancy progresses the foetus develops more like a tiny human being.
A foetus is termed full term between 35 and 38 week of pregnancy. At this time the foetus is sufficiently developed and ready to enter the world. At this stage the foetus measures up to 48 cm to 53 cm. Even though the foetus can move in the womb, at birth the movements are restricted and once out the voluntary movements develop all the way till puberty.