Table 1.

Characteristics of the study population by history of infertility and fertility treatment

Characteristic	No infertility	History of infertility
		No hormone treatment	Hormonal treatment onlya	COS for IVF/ICSIb
	(n = 34,360)	(n = 5948)	(n = 1429)	(n = 1576)
Absolute dense volume, cm3	62.8 ± 33.2	64.0 ± 33.7	64.8 ± 31.4	73.8 ± 41.5
Absolute non-dense volume, cm3	773 ± 466	805 ± 470	804 ± 499	706 ± 465
Percent dense volume, pp	9.2 ± 5.2	9.0 ± 5.2	9.3 ± 5.2	11.4 ± 5.8
Age at mammography, years, %
40–44	20.9	16.4	22.9	42.5
45–49	19.1	17.2	20.4	28.7
50–54	18.3	17.2	19.9	18.3
55–59	13.4	15.1	15.3	8.3
60–64	14.0	16.6	12.5	1.8
65–69	14.4	17.5	9.0	0.3
BMI, kg/m2, %
<18.5	0.8	1.0	1.0	1.4
18.5–24.9	55.7	53.6	54.9	61.7
25–29.9	30.9	32.6	29.5	27.0
≥30	12.6	12.8	14.6	9.8
Age at menarche, years, %
<12	12.6	14.2	14.1	16.1
12–14	72.0	70.5	69.7	70.7
≥15–25	15.3	15.3	16.2	13.2
Cigarette smoking, %
Never	48.7	46.0	50.7	57.4
Current	11.3	10.8	9.2	7.2
Former	40.0	43.2	40.2	35.3
Alcohol consumption, g/d, %
Non-drinker	18.3	17.3	17.4	15.5
0.1–9.9	62.1	61.2	62.8	67.8
≥10	19.5	21.5	19.9	16.7
Education level, %
Compulsory school	10.9	12.0	6.9	2.5
Upper secondary school	31.6	31.1	32.4	25.5
University	54.3	53.1	56.8	69.2
Other	3.2	3.9	3.9	2.8
Family history of breast cancer, %	12.5	12.7	13.6	12.1
Parity, %
Nulliparous	10.8	17.3	14.4	31.3
One birth	12.3	19.3	21.6	27.5
Two births	50.4	44.2	43.5	31.5
Three or more births	26.6	19.2	20.4	9.7
Premenopausal, %	46.1	39.3	50.2	73.9

Plus-minus values are means ± standard deviation

Abbreviations: BMI body mass index, COS controlled ovarian stimulation, HRT hormone replacement therapy, ICSI intracytoplasmic sperm injection, IVF in vitro fertilization, pp percentage points

^aHormonal treatment includes ovulation induction with clomiphene citrate or low-dose gonadotropins

^bCOS for IVF/ICSI treatment includes high-dose gonadotropin stimulation for multiple follicle recruitment and superovulation