Preterm birth and related complications are the most significant cause of perinatal mortality and disability. Aim: to assess the impact of undifferentiated connective tissue dysplasia (UCTD) on the course of the threat of premature birth. Materials and methods. A clinical and instrumental study of the contractile activity of the uterus, isthmus area was carried out using hysterography, uterine tonus measurement, sonography and cervical resistometry. Results. It has been established that the most objective idea of the clinical threat of premature birth in women with UCTD syndrome can be obtained by evaluating the contractile activity of the uterus and the condition of the isthmic-cervical area. It has been proven that the concept of providing assistance at the risk of premature birth in women with UCTD should be differentiated taking into account the activity of the uterus and the functional state of the isthmic-cervical area. Conclusion. The basis of the pathogenesis of the threat of premature birth in women with UCTD syndrome is an isthmic-cervical insufficiency. For the purpose of early diagnosis of isthmic-cervical insufficiency on the background of dysplasia, a sonographic examination of the isthmic-cervical area in the dynamics of the gestational process should be carried out, starting from the early stages of pregnancy.