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.
The interval of gestation period in humans is estimated to be around 40 weeks or 280 days. Gestation period in humans may normally last from 37 to 42 weeks or between 259 and 294 days. That means that in average pregnancy the birth occurs during this period of time. This is considered to be healthy pregnancy.