Antenatal and intrapartum risk factors associated with fetal hypoxia in labor

Objective: To identify the risk factors associated with fetal hypoxia in labor. Materials and methods: A prospective cohort study included 657 women. Of them, 119 women delivered babies with fetal hypoxia at birth and were included in the study group. Cases without fetal hypoxia (n=538) constituted the control group. The diagnosis of fetal hypoxia at birth was verified by determining the acid-base composition of the arterial cord blood. Criteria for acidosis were pH<7.12 and/or BE≥12.4 mmol/L. To identify risk factors for fetal hypoxia in labor, we compared age, patient anthropometric parameters, medical history, and pregnancy complications by collecting anamnesis, studying ambulatory records and physical examination, as well as the characteristics of labor and delivery modes during labor management, evaluating fetal monitoring, and determ ining the composition of the blood acid- base. Results: Patients in the fetal hypoxia group were more likely to have anemia in the first half of pregnancy, gestational diabetes mellitus, extragenital infections, edema of pregnant women, placental insufficiency, and fetal growth restriction. Hypertensive complications of pregnancy as an indication of induction of labor were observed more frequently in the fetal hypoxia group [3 (0.6%) vs 7 (5.9%), p=0.0006]. Gestational age 37-38 and 41 weeks or more at delivery was more common in the fetal hypoxia group, while gestational age 39-40 weeks at delivery was more common in the control group. There were no differences in the rates of preterm prelabor rupture of membranes (9.9 and 13.4%), amniotomy (15.1 and 9.2%), epidural analgesia (51.3 and 55.5%), and mean length of ruptured membranes. Tachysystole was more common in the fetal hypoxia group (RR=7.12 (95% CI 4.8; 10.5), p<0.0001). The relative risk of fetal hypoxia in the presence of labor dystocia was RR=3.17 (95% CI 2; 5), p<0.0001, oxytocin labor stimulation was rR=1.6 (95% CI 1.3; 2), p<0.0001. Conclusion: Antenatal risk factors have low specificity. Intrapartum risk factors including gestational age 37-38 weeks, 41 weeks or more, labor dystocia, oxytocin, labor stimulation, and tachysystole have higher predictive value, especially when combined with CTG. However, in the presence of clinical intrapartum risk factors, the absence of a pathological type of CTG does not guarantee an asphyxia-free birth. Intrapartum risk factors are modifiable in most cases. A rational choice of gestational age and method of labor induction and careful labor management are the reserves for reducing the incidence of fetal hypoxia in labor.

fetal hypoxia, perinatal asphyxia, risk factors