1946	1958	1970	1984	1990
Chloroform	17	0	0	0	0
Nitrous oxide and air	16	56	2	0	0
Nitrous oxide and oxygen	0	0	52	54	60
Trilene	0	25	7	0	0
Pethidine	0	56	69	36	37
Epidural or spinal	0	3	9	17	18
Non-drug pain relief	0	1	2	13	58
No pain relief	68	34	2	2	NR