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,[21] 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.[22] Brain stem activity has been detected as early as 54 days after conception,[23] and the first measurable signs of EEG activity occur in the 12th week.[24] Some fingerprint formation occurs from the beginning of the fetal stage.[25]

Embryo at 6 weeks after fertilization[26]

Fetus at 8 weeks after fertilization[27]

Fetus at 18 weeks after fertilization[28]

Fetus at 38 weeks after fertilization[29]

One way to observe prenatal development is via ultrasound images. Modern 3D ultrasound images provide greater detail for prenatal diagnosis than the older 2D ultrasound technology.[30] Whilst 3D is popular with parents desiring a prenatal photograph as a keepsake,[31] both 2D and 3D are discouraged by the FDA for non-medical use,[32] but there are no definitive studies linking ultrasound to any adverse medical effects.[33] The following 3D ultrasound images were taken at different stages of pregnancy:

3-inch fetus (about 14 weeks gestational age)

Fetus at 17 weeks

Fetus at 20 weeks