When a solid turns into a liquid it is called fusion, more commonly referred to as melting. When a material moves from one state of matter into another it is called a phase transition. Fusion is just...
Human pregnancy can be divided roughly into three trimesters, each approximately three months long. The first trimester is from the last period to the 13th week, the second trimester is from the 14th to 27th week, and the third trimester is from the 28th week to the 42nd week. In humans, birth normally occurs at a gestational age of about 40 weeks, though it is common for births to occur from 37 to 42 weeks.
In the first trimester, gestational sac mean diameter and crown-rump length measurements have become the primary means of evaluating gestational age. 15, 16, 17, 18, 19 In the second and third trimesters, fetal head, body, and extremity measurements have been commonly used to assess gestational age. Physical examination also tends to be inaccurate, especially with advancing gestational age. 10 Bimanual examination in the first trimester may be accurate within Â±2 weeks; however, fundal height measurement, which is more commonly used to assess gestational age, is only accurate within Â±4 to 6 weeks.