Variation in breast cancer risk associated with factors related to pregnancies according to truncating mutation location, in the French National BRCA1 and BRCA2 mutations carrier cohort (GENEPSO)

Table 4 Variation of BC risk associated with full-term pregnancies and incomplete pregnancies according to location of the truncating mutation in BRCA1.

Reproductive factors	Location of truncating mutation in *BRCA1*mutation carriers
	Outside LR1 (16,690 person-years of follow-up)					In LR1 (5,367 person-years of follow-up)
	Person-years^a	No. of cases^a	HR	95% CI	P value	Person-years^a	No. of cases^a	HR	95% CI	P value
Parity^b
Nulliparous	10,911	21	1.00			3,378	9	1.00
Parous	5,779	145	1.42	0.77-2.63		1,989	34	0.27	0.13-0.55	<10^-3
No. of full-term pregnancies^b
0	10,911	21				3,378	9	1.00
1-2	4,218	108	1.63	0.88-3.05		1,354	23	0.32	0.15-0.68	<10^-3
≥3	1,546	36	0.96	0.48-1.94		635	11	0.20	0.08-0.49	<10^-3
Full-term pregnancies by attained age^b
Nulliparous	10,911	21	1.00			3,378	9	1.00
Before age 40	4,325	81	1.36	0.72-2.56		1,501	23	0.33	0.16-0.68	<10^-3
After age 40	1,439	63	1.49	0.70-3.19		488	11	0.21	0.09-0.51	<10^-3
Incomplete pregnancies ^c
Never	14,247	92	1.00			4,419	23	1.00
Ever	2,404	73	1.43	0.98-2.07	0.06	948	20	0.95	0.47-1.96
No. of incomplete pregnancies ^c
0	14,247	92	1.00			4,419	23	1.00
1-2	2,254	66	1.36	0.93-2.00		820	16	0.82	0.39-1.73
≥3	150	7	2.59	1.24-5.40	0.01	128	4	2.05	0.48-8.76
Type and length of incomplete pregnancies ^c
No incomplete pregnancies	14,204	92	1.00			4,419	23	1.00
Induced abortion only	1,279	40	1.49	0.95-2.36	0.08	431	5	0.65	0.21-2.00
Miscarriage with length ≤3 months	924	28	1.33	0.79-2.26		428	13	1.25	0.56-2.81
Miscarriage with length >3 months	153	4	1.12	0.35-3.59		46	2	1.52	0.18-12.5

^aNot including missing data. ^bAdjusted for menopausal status (yes, no) and oral contraceptives (never, ever). ^cAdjusted for parity (0, 1, 2, ≥3), menopausal status (yes, no) and oral contraceptives (never, ever). HR, hazard ratio; CI, confidence interval.

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