Doppler evaluation of blood flow in fetal inferior vena cava during 48-hours Atosiban administration in spontaneous preterm labor.

OBJECTIVES: The aims were to evaluate whether any changes in blood flow in fetal inferior vena cava (IVC) are observed during Atosiban tocolysis within the first 48 hours of therapy.

METHODS: Detailed Doppler evaluation of blood flow in fetal IVC was performed prior to Atosiban administration and after 24 and 48 hours respectively. Maternal and fetal heart rate was assessed. IVC Doppler indices, such as, S/D (systole/diastole), PVIV (peak velocity index for the vein) and PLI (preload index) were calculated. To determine changes over time in all study variables, analysis of variance (ANOVA) for repeated measurements was used and followed by Tukey-Kramer's post hoc test. The effects of additional clinical covariates were checked.

RESULTS: Maternal heart rate was not altered significantly during Atosiban administration. No significant changes in FHR (fetal heart rate) as well as following IVC Doppler parameters (S/D, PVIV) were recorded after 24/48 hours of tocolytic treatment. The fetal IVC PLI values were significantly reduced after 24 hours and 48 hours of treatment. The changes in PLI values when comparing 24 and 48 hours results were not statistically significant.

CONCLUSIONS: As the questions about drug safety appeared after the animal study had been published about possible myocyte injury, detailed Doppler evaluation of IVC blood flow was performed. It revealed the changes in preload conditions which could be a reflection of successful Atosiban tocolytic treatment. No hemodynamic changes in IVC were noted, suggesting the presence of fetal acidemia due to possible heart damage was observed.

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