Table 1. Growth and development in triple X syndrome according to the results of unbiased studies.

	Children <6 years of age15, 19	School children16, 20	Teenage girls17, 21	Adolescents and (young) adults18, 22, 27, 28, 30, 31, 32
Physical growth	Average maternal age: 33 years. Mean birth weight 400–500 g lower. Appearance at birth: normal. Head circumference: below 50th%. Height: almost all are above 50th%.	Increased growth velocity between 4 and 8 years of age. Height is often above 75th%. Leg length significantly increased. Increase in weight less than in height. Bone age 1 SD below normal.	No summarized data. Differences between cases and controls seem to decrease.	No summarized data.
Motor development	Milestones of motor development may be delayed.	Sensory–motor–visual integration problems	Gross and fine motor development continues to be below that of controls.	Adult cases cope with coordination problems by seeking appropriate jobs.
Intellectual development.		Verbal IQ: 69.6% below 90. Performance IQ: 41.2% below 90.	Verbal IQ: 86.63 (19.01.points lower than controls) Performance IQ: 95.19 (14.41 points lower than controls)	IQ findings in adults are in the same range as far as they have been assessed.
Receptive and expressive language development	In half of the cases delayed.	Some language difficulties in 75% of cases	Poor language skills continue to interfere with development.	Language problems continue as far as they have been assessed.
Social and behavioural development.	Some cases show temper tantrums.	Difficulties in forming good interpersonal relationships.	Behavioural problems noted as often in cases as in controls. Sensitivity to (un)stable family functioning.	Adult cases sometimes show problems in establishing satisfying relationships. Low self-esteem.
Educational development		Educational problems in 74.1% in cases and 44.4% in controls.	Educational problems in 71.4% in cases and 31.0% in controls.	After leaving school, cases seem to feel better.