Table 1.

Characteristics of the study population (n = 808 834)

	ART women, n= 16 626				Controls, n= 792 208				Total Cohort
	All		Breast Cancer		All		Breast Cancer		All
	n	%	n	%	n	%	n	%	n	%
Age at entry
< 25	495	3	1	1	316 408	40	1 445	18	316 903	39
25-29	4 022	24	22	16	282 199	36	2 843	36	286 221	35
30-34	7 550	45	59	43	141 139	18	2 304	29	148 689	18
35-39	4 208	25	54	38	45 146	6	1 092	14	49 354	6
40-44	341	2	2	1	7 049	1	208	3	7 390	1
≥45	10	0	0	0	267	0	7	0	277	0
Total	16 626	100	138	100	792 208	100	7 899	100	808 834	100
Parity at entry
P0	12 538	75	96	70	630 967	80	4 570	58	643 505	80
P1	3 333	20	35	25	95 211	12	1 912	24	98 544	12
P2+	755	5	7	5	66 030	8	1 417	18	66 785	8
Total	16 626	100	138	100	792 208	100	7 899	100	808 834	100
Parity at exit*
1	7 612	46	59	43	178 980	23	1 240	16	186 592	23
2	6 970	42	62	45	343 918	43	3 549	45	350 888	43
3	1 696	10	13	9	197 833	25	2 315	29	199 529	25
≥4	348	2	4	3	71 477	9	795	10	71 825	9
Total	16 626	100	138	100	792 208	100	7 899	100	808 834	100
Calendar year at entry
1983-1992	1 383	9	40	29	363 350	46	6 471	82	364 773	45
1993-2002	6 233	38	89	64	244 461	31	1 316	17	250 783	31
2003-2010	8 872	53	9	7	184 397	23	112	1	193 278	24
Total	16 626	100	138	100	792 208	100	7 899	100	808 834	100
Method of ART
IVF	10 112	61	111	80	-	-	-	-	10 112	61
ICSI	4 968	30	11	8	-	-	-	-	4 968	30
Combination/Missing/Unknown	1 546	9	16	12	-	-	-	-	1 546	9
Total	16 626	100	138	100	-	-	-	-	16 626	100
Age at first diagnosis
< 30	-	-	0	0	-	-	129	2	-	-
30 - 39	-	-	36	26	-	-	1 694	21	-	-
40 - 49	-	-	80	58	-	-	4 010	51	-	-
50 - 59	-	-	21	15	-	-	1 934	24	-	-
≥ 60	-	-	1	1	-	-	132	2	-	-
Total	-	-	138	100	-	-	7 899	100	-	-
Region of present residence
South East	5 265	32	40	29	266 553	34	2 746	35	271 818	34
Oslo	2 514	15	25	18	123 231	16	1 229	16	125 745	16
South	3 018	18	24	17	114 651	14	1 088	14	117 669	15
West	2 702	16	20	14	135 481	17	1 358	17	138 183	17
Middle	1 780	11	16	12	68 834	9	634	8	70 614	9
North	1 344	8	13	9	83 086	10	840	11	84 430	10
Missing or unknown	3	0	0	0	372	0	4	0	375	0
Total	16 626	100	138	100	792 208	100	7 899	100	808 834	100

^*Number of births per woman at the end of follow up