The association of inflammatory changes of the uterus and chorioamniotic membranes with different types of labor activity anomalies.

Objective: Aim: To clarify the association between different types of uterine contractility dysfunction and the inflammation of the uterus and chorioamniotic membranes.

Patients and methods: Materials and Methods: The association between the inflammation of the uterine layers, chorioamniotic membranes, umbilical cord, and different types of labor activity abnormalities was examined in 382 patients with singleton pregnancies at 28-42 weeks' gestation who underwent Caesarean section (CS) for abnormal uterine contractions and other complications. Statistical analyses included the Mann-Whitney U, Chi-squared test, and logistic regression.

Results: Results: In the control group, slight infiltration with polymorphonuclear leukocytes (PMNs) and macrophages of the myometrium and decidua of the lower uterine segment at term pregnancy was found in 59.7% and 73.6% of cases. The main clinical risk factors for placental and decidual membrane inflammation in patients with excessive uterine activity (EUA) were prematurity, multiparity, group B streptococcus (GBS) colonization, and duration of ruptured fetal membranes before the CS. Moderate or marked myometrial inflammation of both uterine segments in the EUA group was diagnosed only in patients with cervical dilation of >6 cm and duration of labor of >8h. In women with hypotonic uterine activity (HUA), decidual and myometrial inflammation was significantly associated with nulliparity and intrapartum factors, such as protracted active first stage of labor, advanced cervical dilation, and number of vaginal examinations. In all cases, inflammation of the myometrium was accompanied by deciduitis.

Conclusion: Conclusions: Mild inflammation of the decidual membrane and myometrium of the lower segment at term pregnancy is a common physiological phenomenon contributing to labor initiation. Uterine hyperfunction comes as the response of the unaffected myometrium to the release of high concentrations of proinflammatory cytokines produced by the inflamed decidual and chorioamniotic membranes into the bloodstream. Marked myometrial inflammation that occurs in prolonged labor is an additional factor aggravating the hypotonic uterine activity.