The crown-rump length is 32 to 54 mm . The fetus aquires human shape and the fetal body comes longer .The head is still disproportionally large . The forehead prominent and the occiput is flat . The cerebel hemispheres can be seen at 9 weeks . Ossification starts from the occipital bone at 10 weeks . The cortex is about 1 mm thick . The lateral ventricles occupy completely the anterior part of the head and cover the diencephalon . The mesencephalon gradually moves towards the middle of the brain , the 3rd ventricle becomes narrow , the cerebellar hemispheres fuse in the midline 11 to 12 weeks .
Fetal heart rate is around 165 beats per minute . The motion of the atrioventricular valves and the atrial and ventricular septa may be visible at 10 weeks . All cardiac structures can be visualized at the end of the 11th week .
Maximum herniation of the bowel is detectable at the beginning of the 10th week (starting at the end of the 8th week ) .
The ossification centers of the spine and the long bones start being visible at 10 weeks . The ossification of the spine begins at the level of the cervical vertebrae and spreads caudally to the thoracic and lumbosacral areas during weeks 12 and 13 . Ossification of the metacarpals and metatarsals can be identified at 12 weeks . The digits and sometimes the toes become visible from 11 weeks .