Prenatal development and sonograph images

Prenatal development is divided into two primary biological stages. The first is the embryonic stage, which lasts for about two months. At this point, the fetal stage begins. At the beginning of the foetal stage, the risk of miscarriage decreases sharply, all major structures including hands, feet, head, brain, and other organs are present, and they continue to grow and develop. When the fetal stage commences, a fetus is typically about 30 mm (1.2 inches) in length, and the heart can be seen beating via sonograph; the fetus bends the head, and also makes general movements and startles that involve the whole body. Brain stem activity has been detected as early as 54 days after conception,and the first measurable signs of EEG activity occur in the 12th week. Some fingerprint formation occurs from the beginning of the fetal stage.

Embryo at 6 weeks after fertilization	Fetus at 8 weeks after fertilization	Fetus at 18 weeks after fertilization	Fetus at 38 weeks after fertilization
Relative size in 1st Month (simplified illustration)	Relative size in 3rd Month (simplified illustration)	Relative size in 5th Month (simplified illustration)	Relative size in 9th Month (simplified illustration)
7 weeks	13 weeks	17 weeks	20 weeks