A debate about ultrasound and anatomic aspects of the cervix in spontaneous preterm birth

Preterm birth is the legal first global cause of neonatal death. The cervix has two roles: it has to stay closed to allow the fetus to undergo a normal development during gestation, and at term, the cervix has to dilate under the pressure of uterine contractions to allow the delivery. The purpose of this article is to establish if the ultrasound measured length of the cervix and its appearance are predictive for the spontaneous preterm birth. Cervical insufficiency can be described by painless cervical dilatation leading to pregnancy losses/ births, with no other risk factors present. During gestation, the physiological softening of the cervix is determined by the extracellular matrix components, particular decorin, and thrombospondin 2. The direction of the collagen fibers remains the same - circumferential direction, but the collagen solubility increases. Therefore, during pregnancy, the cervical tissue is more hydrated and has higher collagen extractability than non-pregnant tissue. Women with cervical incompetence have increased levels of smooth muscle cells than normal pregnant women, the number of elastic fibers is low, and also the concentration of hydroxyproline is decreased. Transvaginal ultrasound is the suitable gold standard exam that can offer essential information about the cervical length and state of the internal os in early asymptomatic stage of cervical insufficiency for predicting and preventing preterm birth. In our experience, a transvaginal ultrasound screening for the measurement of the cervix is required. We consider that the proper gestational age for the prediction of a preterm birth is at 18-22 weeks of gestation for the general population and earlier for patients with a history of preterm birth. Just from an observational point of view, we concluded with the fact that the cerclage of the cervix is unnecessary if the cervical length is above 2 cm and if the internal cervical os is closed. In the absence of funneling, the probability of cervical incompetence is low and the best prophylactic option is progesterone administration.