MR imaging of uterine morphology and dynamic changes during lactation

Purpose: To investigate the influence of lactation and ovarian hormones on uterine morphology and function by comparing uteruses of lactating women with nulliparous women on MRI. Materials and Methods: Sagittal T2WI and cine MR images were obtained with 1.5 Tesla (T) and 3T scanner from 22 lactating women and 16 nulliparous women as a control group. The lactating group was further divided into amenorrhea and menorrhea subgroups. Uterine area, endometrial thickness, junctional zone (JZ) thickness, relative signal intensity (rSI) of the JZ, and of the outer myometrium (OM), were measured on T2-weighted fast spin echo images as static image parameters. Frequency of peristalsis (/3min), degree of endometrial transformation, subendometrial conduction, outer myometrial (OM) conduction, and sporadic myometrial contraction were evaluated using cine MR images. The above image parameters were compared between the lactating group and the control group, and between the lactational amenorrhea group and the lactational menorrhea group as a sub-analysis. Results: A significant difference was observed in all the static image parameters and in three of the five cine image parameters between the lactating group and the control group (P < 0.01). In sub-analysis, a statistical significance was found between the lactational amenorrhea group and lactational menorrhea group in area of the uterus and both endometrial and JZ thickness (P < 0.05), but not in cine image parameters (P = 0.682, P = 0.096, P = 0.191, P = 0.939, P = 0.289, respectively). Conclusion: Uterine appearance and peristalsis were different between lactating and nulliparous women. The morphological differences were pronounced between lactating amenorrhea and menorrhea women. Level of Evidence: 2. J. Magn. Reson. Imaging 2017;45:617–623.