A child in the third trimester of pregnancy is generally called a fetus and can usually be detected under ultrasound guidance if the fetus is developing normally within the mother’s body. In the third trimester, the fetus already has the shape of a human body, with a fetal length of about 87mm, a fetal weight of about 18g, and a foot length of about 14mm. The appearance, limbs, organs, and bones of the fetus have begun to develop and gradually take shape. 1. Appearance features: the tail of the fetus in the third trimester has completely disappeared, the head and limbs have developed, the fetal head accounts for about 1/3 of the overall length, the cheeks, jaws, eyelids, and the auricles have basically developed and shaped; 2, the formation of limbs: the third trimester fetal limbs have developed, you can see clear fingers, toes and finger nails, the limbs have movement appear, can move in the amniotic fluid; 3, the formation of organs: the third trimester fetal organs have basically formed, you can see the subcutaneous blood vessels and internal organs, the heart, liver, stomach, intestines, kidneys and other internal organs development, and organs have begun to work to maintain life activities, but the development of each organ is not yet perfect; 4, skeletal development: the development of fetal skeletal cells accelerates in the third trimester, the body length gradually becomes longer, and with the deposition of calcium salts, the bones gradually calcify and harden. The third trimester is a critical period for fetal development, the mother needs to consume enough nutrients to meet the developmental needs of the fetus, pay attention to balanced nutrition during pregnancy, ensure adequate calcium intake to promote bone development, maintain emotional stability and avoid bad moods.