Table 1.

Summary of cytogenetic data

	No.	%a
Total patients	530	100
Fail	80	15
Normal	39	7
Abnormal	411	78

Abnormality	No.	%b
iAMP21 alone	84	20
Gain of 21	10	3
Gain of iAMP21	4	1
Gain of X	86c	21
Monosomy 7	19	5
Trisomy 10	18	4
Trisomy 14	17	4
Monosomy 15		3
abn1q	43	11
abn6q	18	4
abn7q	46	11
abn7q/-7	65d	16
abn9p	42e	10
abn11q	50f	12
abn12p	46g	11
abn13q	22	6
abn16q	26	6

Abbreviations: abn1q, abnormalities involving 1q; abn6q, abnormalities involving 6q; abn7q/-7, monosomy 7 plus abnormalities involving 7q; abn9p, abnormalities involving 9p; abn11q, abnormalities involving 11q; abn12p, abnormalities involving 12p; abn13q, abnormalities involving 13q; abn16q, abnormalities involving 16q; iAMP21, intrachromosomal amplification of chromosome 21.

^aPercentage of total cases.

^bPercentage of cases with an abnormal karyotype.

^cA total of 49 males and 27 females.

^dCombined numbers for abn7q and monosomy 7.

^eFluorescence in situ hybridisation (FISH) confirmed deletion of 9p in two cases with an abnormal karyotype.

^fFISH confirmed deletion of 11q in four cases with an abnormal karyotype.

^gFISH confirmed deletion of 12p in 14 cases with an abnormal karyotype.