There are also established norms for head size as it increases with age. Microcephaly refers to a head circumference less than the 2nd percentile. Macrocephaly refers to a head circumference greater than the 98th percentile. These are best assessed by looking directly downwards at the top of the head. The diagnosis of fetal alcohol syndrome is partly based on craniofacial features which include microcephaly, telecanthus, narrow palpebral fissures, thin lips and a flat philtrum, with or without cleft lip or palate.
All fingers have two creases except for the thumb which has one.
Occasionally the fifth digit has only one crease because of a small middle phalanx. The palm has two horizontal creases and an oblique crease created by thumb to finger apposition. These creases are usually present by the twelfth week in utero. Skin and hair abnormalities are important. A milder form of spine abnormality, spine bifida occulta, refers to a hidden spine defect apparent only because a tuft of hair is present on the overlying skin along with a waddling or abnormal gait.