The degree of clarity in the assessment of the surface anatomy increases gradually from first trimester to 35 weeks , thereafter it plateau till term due to decrease in amniotic fluid volume and the relative size of the fetal parts.
As early as 12 weeks a prominent forehead is visible. It may look exaggerated to parents but this is normal procencephalon development and parents should be reassured that the ratio between the head and the body will decrease as pregnancy advances. The ear buds have developed into pinnae and both four limbs have identifiable digits. The neck is shirt and shoulders are close to the body. A true cephalothorax never exist in human development The abdomen is closing although in many situations a physiological umbilical hernia will still be present at 13 weeks.
Fetal fingers and limb anatomy can easily be visualized in 3D and poses no doubt to the parents about the normality of the baby.