Preliminary report of 48-hours Atosiban administration in spontaneous preterm labor - Doppler blood flow assessment of placental and fetal circulation.

OBJECTIVES: The aims were to investigate whether there are any changes in placental and fetal circulation during Atosiban tocolysis within the first 48 hours of therapy.

METHODS: Detailed Doppler evaluation of placental and fetal circulation was performed prior to Atosiban administration and thereafter at 24 and 48 hours. Maternal heart rate and the pulsatility index (PI) in both uterine arteries (R-UtA, L-UtA) were assessed. Fetal heart rate (FHR), the resistance (RI) and pulsatility index (PI) of umbilical (UA) and middle cerebral artery (MCA) were measured. Additionally cerebroplacental ratio was calculated. E-wave/A-wave ratio (E/A) for atrioventricular valves, the myocardial performance index (MPI) and shortening fraction (SF) for both ventricles were calculated for both ventricles independently. To determine changes over time in all study variables analysis of variance (ANOVA) for repeated measurements followed by Tukey-Kramer's post hoc test was used. The effects of additional clinical covariates were checked.

RESULTS: Maternal heart rate and blood flow in (R-UtA/L-UtA) were not altered significantly during Atosiban administration. No significant changes in FHR as well as Doppler parameters (RI, PI, PSV) in UA and MCA were recorded after 24/48 hours of tocolytic treatment. The mean values of cerebroplacental ratio (CPR) remained unaltered during treatment. Detailed evaluation of fetal cardiac function parameters (E/A, SF, MPI) calculated independently for both ventricles, revealed no significant changes over the time.

CONCLUSIONS: To our best knowledge this study has been first evaluation of placental and fetal circulation with assessment of cardiac hemodynamic function during 48-hours administration of Atosiban. This kind of tocolysis treatment seems not to alter uterine nor fetal arterial blood flow pattern seriously. Hemodynamic cardiac activity in fetuses has remained unaffected. We cannot conclude definitely that there are absolutely no changes in the fetal hemodynamic condition due to Atosiban. Further studies should be performed to verify its possible influence on fetal venous blood flow.