 The internal contractile measure was the strength of the contractions based upon the sum of the contraction amplitudes measured at the anterior and posterior endometrial myometrial interfaces. The amplitude at each interface was defined as the average difference between the endometrial myometrial-lumenal distance measured at the peaks and troughs of the endometrial myometrial interfaces. The internal contractile measure was reported in mmcontraction. The internal contractile measure quantified the movement of the endometrium relative to the lumen, i.e. the motion internal to the uterus. 