First Trimester

First Trimester : (Period from fertilization to 12th week) It is the period of the most radical changes in both mother and embryo. In the first 2–4 weeks, the embryo receives nutrients directly from the endometrium. This is the main period of organogenesis, the development of the body's organs; by the end of eight weeks, the major structures found in the adult body have already formed in the embryo, in rudimentary form, and from this point onward the embryo is called a foetus. By this stage the foetus is about 3 cm long: arms, hands, fingers, feet and toes are formed, and it can open and close its mouth and fists. The central nervous system is fully formed, and the excretory and circulatory systems begin working; foetal movements begin, though the mother cannot yet feel them, and a heartbeat can be detected from around the 6th week. By the end of the first trimester the foetus is about 7–10 cm long. …