Cardiotocography in the diagnosis of meconium aspiration syndrome

Meconium aspiration is one of the most severe and unpredictable complications of pregnancy and delivery for both obstetricians and neonatologists. This syndrome involves the aspiration of meconium-stained amniotic fluid into the fetal respiratory system, potentially leading to lung pathology and respiratory distress syndrome. Despite advances in neonatal care, mortality rates for this condition range from 1% to 4%.The objective: to improve early diagnosis of meconium aspiration syndrome by identifying specific features of fetal monitoring curves and data from fetal pulse oximetry. Materials and methods. The cardiotocography curves and fetal tissue oximetry data from 71 deliveries which were complicated by meconium-stained amniotic fluid were analyzed. The patients were divided into two groups: the main group (MG) – 39 women whose newborns were diagnosed with meconium aspiration syndrome (MAS), and 32 women with meconium-stained amniotic fluid whose newborns had no signs of MAS formed the control group (CG).Measurements of fetal scalp tissue oxygen saturation (rSO2) were conducted during the first 30 minutes of the patient’s stay in the delivery room and during the last 30 minutes before the birth of the child. In each group, the frequency of rSO2 values ≤ 30%, 31–70%, and > 70% was analyzed at both the initial and repeat measurements.Results. The average duration of labor in the MG was 585.7 ± 102.3 minutes, compared to 314.8 ± 98.9 minutes in the CG, indicating prolonged labor in cases with MAS. Reduced variability lasting up to 10 minutes was observed in 61.5% of cases in the MG vs 28.1% in the CG during the first four hours of labor. Episodes of reduced variability of varying durations were significantly more prevalent in the MG from 241 to 960 minutes of labor. Complicated decelerations were more typical in the MG compared to the CG – 23.0% complicated decelerations lasting till 10 minutes and 23.0% – lasting less 30 minutes in the MG vs 9.3% and 6.2%, respectively, in the CG during the first four hours of labor. Uncomplicated decelerations of shorter durations (till 10 minutes) were more typical in the MAS group (30.7 vs 9.3% in the CG during the first 240 minutes; 40.0 vs 4.1% during the next four hours). In contrast, longer uncomplicated decelerations (more than 10 minutes) were more typical in the CG (7.7 vs 50.0% during the first four hours; 10.0 vs 83.3% in the following four hours). Fetal oximetry revealed significantly lower rSO2 values in the MG compared to the CG, particularly during the last 30 minutes before delivery (51.3 vs 31.3%, respectively).Conclusions. Reduced heart rate variability lasting over 10 minutes was more typical for women whose newborns were diagnosed with MAS. Deliveries complicated by MAS were characterized by both complicated decelerations of any duration and shorter uncomplicated decelerations. Fetuses diagnosed with MAS after birth exhibited rSO2 levels below 30.0% in 38.5% of cases at the beginning of labor and in 51.3% of cases during the last 30 minutes of labor (compared to 25.0% and 31.0%, respectively, in fetuses without MAS).