Prospective evaluation of the ultrasound appearance of the endometrium in a cohort of 1,186 infertile women  Christian De Geyter, M.D., Matthias Schmitter, Maria De Geyter, Ph.D., Eberhard Nieschlag, M.D., Wolfgang Holzgreve, M.D., Hermann P.G Schneider, M.D.  Fertility and Sterility  Volume 73, Issue 1, Pages 106-113 (January 2000) DOI: 10.1016/S0015-0282(99)00484-7

Figure 1 The reproducibility of sonographic measurements of endometrial thickness was established by having two examiners evaluate each of the 23 patients (A), by comparing the endometrial thickness on 2 consecutive days at the end of the follicular phase in 952 patients (B), and by comparing the endometrial thickness on the day of ovulation induction in different cycles in 343 patients (C). The comparisons are presented graphically according to the method described by Bland and Altman (20), in which the difference between both values is plotted against the mean of both values. The thick horizontal line represents the mean of the differences, whereas the thin horizontal lines represent the corresponding SDs multiplied by two. De Geyter. Ultrasound appearance of endometrium. Fertil Steril 2000. Fertility and Sterility 2000 73, 106-113DOI: (10.1016/S0015-0282(99)00484-7)

Figure 2 The proliferation of the endometrium during follicular development until ovulation induction followed an exponential growth curve. The intercept and the slope of the exponential endometrial growth in conception and nonconception cycles during the ultrashort protocol (A) and the long protocol (B) were not different. De Geyter. Ultrasound appearance of endometrium. Fertil Steril 2000. Fertility and Sterility 2000 73, 106-113DOI: (10.1016/S0015-0282(99)00484-7)