Optical properties, physiologic parameters and tissue composition of the human uterine cervix as a function of hormonal status

The influence of sex hormones on the human uterine cervix is likely to be important in the process of cervical ripening. Frequency domain near-infrared spectroscopy (FD-NIRS) was used to investigate non-invasively the changes in the optical properties that reflect physiologic parameters and tissue composition of the uterine cervix in the different phases of the menstrual cycle. Twenty premenopausal and nine postmenopausal women were examined. Optical properties of the uterine cervix were measured, and physiological parameters [concentration of water, oxyhemoglobin (O₂Hb) and deoxyhemoglobin (HHb), total hemoglobin (tHb), oxygen saturation (StO₂), water, and scattering power] were calculated. Analysis of variance (ANOVA) was used to test for statistical significance. The optical properties of the anterior cervical lip did not differ from those of the posterior lip. HHb was significantly lower in cervices during menstrual bleeding than during the follicular, luteal, or postmenopausal phases. The ratio of O₂Hb to HHb was highly significantly increased by a factor of 2 when cervices during the menstrual bleeding were compared with those during the follicular, luteal, or postmenopausal phases. The scattering power was significantly lower during menstrual bleeding than during the follicular or postmenopausal phases. We demonstrated that withdrawal of sex hormones during menstrual bleeding is associated with a significant decrease in HHb and scattering power, with stable values of O₂Hb, tHb, StO₂, and H₂O compared with the values during the follicular, luteal or postmenopausal phases of the menstrual cycle. Cervical softening during menstrual bleeding seems to be different from cervical softening for labor.