The effect of having an extra X chromosome can be very varied. Some females with triple-X syndrome show no, or very few, symptoms and are entirely 'normal', whilst others have a lot of typical features:
At birth, girls with triple-X syndrome are usually normally developed, although babies may be floppy (hypotonic) and weight may be slightly lower than average. Many girls have a 'growth spurt' up until the age of eight years and women tend to be a little taller than average.
With the 'full blown' condition, girls with triple-X syndrome are at risk of delays in neuromotor development, which can lead to coordination problems including both gross motor skills and/or fine motor skills. Learning ability and/or impaired social relationship skills may also be present. Behavioural problems including tantrums, shyness and emotional immaturity are rather more frequent than in girls with XX chromosomes. Delays in speech and language development are frequent.
Sexual development is normal and triple-X women are fertile though there is a slight increased risk of sex chromosome changes in their children. Individuals with triple-X syndrome have no increased risk of any diseases during childhood or in adult life.