Читать книгу Lifespan Development - Tara L. Kuther - Страница 153

During the fetal period, from the ninth week to birth, the organism, called a fetus, grows rapidly, and its organs become more complex and begin to function. The end of the third month marks the close of the first trimester, at which time all parts of the fetus’s body can move spontaneously, the legs kick, and the fetus can suck its thumb (an involuntary reflex). By the end of the 12th week, the upper limbs have almost reached their final relative lengths, but the lower limbs are slightly shorter than their final relative lengths (Sadler, 2015).