Table 1. Estimated prevalences of carriers of haemoglobin gene variants and affected conceptions.

WHO region	Demography 2003					% of the population carrying				Affected conceptions (per 1000)				Affected births (% of under-5 mortality)
	Population (millions)	Crude Birth rate	Annual births (1000s)	Under-5 mortality rate		Significant varianta	α+ thalassaemiab	Any variantc		Sickle-cell disordersd	Thalassaemiase	Total
African	586	39.0	22 895	168		18.2	41.2	44.4		10.68	0.07	10.74		6.4
American	853	19.5	16 609	27		3.0	4.8	7.5		0.49	0.06	0.54		2.0
Eastern Mediterranean	573	29.3	16 798	108		4.4	19.0	21.7		0.84	0.70	1.54		1.4
European	879	11.9	10 459	25		1.1	2.3	3.3		0.07	0.13	0.20		0.8
South-east Asian	1 564	24.4	38 139	83		6.6	44.6	45.5		0.68	0.66	1.34		1.6
Western Pacific	1 761	13.6	23 914	38		3.2	10.3	13.2		0.00	0.76	0.76		2.0
World	6 217	20.7	128 814	81		5.2	20.7	24.0		2.28	0.46	2.73		3.4

^a Significant variants include Hb S, Hb C, Hb E, Hb D etc. β thalassaemia, α⁰ thalassaemia.
^b α⁺ thalassaemia includes heterozygous and homozygous α⁺ thalassaemia.
^c Allows for (1) coincidence of α and β variants, and (2) harmless combinations of β variants.
^d Sickle-cell disorders include SS, SC, S/β thalassaemia.
^e Thalassaemias include homozygous β thalassaemia, haemoglobin E/β thalassaemia, homozygous α⁰ thalassaemia, α⁰/ α⁺ thalassaemia (haemoglobin H disease).