Table 1.

Population characteristics of the same premenopausal women at two mammograms during different phases in their menstrual cycle

Follicular (N = 204), mean (SD)Luteal (N = 204), mean (SD)Difference (luteal-follicular, N = 204), mean (SD)
Age (y)45.6 (4.2)45.7 (4.1)0.04 (1.2)
Body mass index (kg/m2)25.5 (5.9)25.6 (6.2)0.12 (1.8)
Weight (kg)70.6 (17.6)70.9 (18.2)0.25 (4.6)
Day in menstrual cycle*11.2 (2.4)25.5 (3.5)
Time between exams (d)415.3 (62.9)
Percent breast density35.8 (21.3)36.7 (21.3)0.9% (9.2)
Breast area940.3 (326.9)957.7 (323.6)17.4 (140.9)
Dense area312.1 (211.7)323.6 (200.4)11.5 (97.4)
%%
1st mammogram51.049.0
BI-RADS breast density
    1 (entirely fatty)1.00.5
    2 (scattered fibroglandular)20.923.0
    3 (heterogeneously dense)53.753.0
    4 (extremely dense)24.423.5
  • NOTE: Menstrual cycle: follicular = days 7 to 15 or week 2 of cycle; luteal = days 21 to 35 or week 4 of cycle.

  • * Available for 130 women with continuous data; 74 women reported week in menstrual cycle.

  • Mean absolute value of the difference.