Table 1.

Frequency of ART in children with four imprinting disorders and observed/expected ratios of ART in the same groups

	The percentage of patients after ART/total: % (n) (2015)	Observed/expected ratios of ART
BWS	6.0% (7/117)	4.46
AS	1.8% (4/227)	1.32
PWS	4.6% (24/520)	3.44
SRS	11.9% (8/67)	8.91

Results of a nationwide epidemiological investigation of four imprinting disorders in Japan, under the governance of the Ministry of Health, Labor and Welfare of the Japanese government. Whether the patient was born after ART treatment was confirmed in a questionnaire. The number of patients was expected by multiplying the total number of disease patients by the live birth rate after ART (1.34%) from 1985 through 2015 in Japan (http://plaza.umin.ac.jp/~jsog-art/)