Oxidative stress is recognized as a important factor in the pathogenesis premature birth. Preterm birth is defined as delivery before 37 completed weeks of gestation and it is the leading cause of neonatal morbidity and mortality. The investigators conducted this analysis to investigate the safety of administration of Atosiban - a reversible, competitive antagonist of the oxytocin receptor in the treatment of preterm labor and its impact on the level of oxidative stress after 48 hours of tocolytic treatment.

Atosiban (1-(3-mercaptopropanoic acid)-2-(O-ethyl-D-tyrosine)-4-L-threonine-8-L-ornithine-oxytocin) is licensed for clinical use in women suffering from threatened premature birth and is widely used in clinical practice in Europe because of its low side effect profile. The impact of Atosiban on pregnancy outcomes in women has been investigated in recent years and the research has shown its ability to reduce intracytoplasmic calcium release and downregulate prostaglandin synthesis as oxytocin receptor antagonist. While a role of Atosiban in the modulation of myometrial contractility is well-described, its effect on many other functions is not so well known.

The serum and plasma samples take for the measurement of total oxidant status (TOS), total antioxidant status (TAS), level of 3-nitrotyrosine (3-NT), and carbonyl and thiol groups will be stored at -70°C in aliquots for subsequent biochemical analysis and processed within two months.

Inclusion Criteria:

• pregnant women between 24-35 weeks' gestation receiving prenatal care due to the risk of premature birth
• intact membranes
• evidence of premature labor (regular, painful and persistent uterine contractions; cervical changes)

Exclusion Criteria:

• acute fetal distress
• other conditions requiring immediate delivery (eclampsia and severe pre-eclampsia, placenta previa, abruptio placenta)
• vaginal bleeding,
• premature rupture of membranes
• chorioamnionitis,
• fetal congenital malformations,
• intrauterine growth restriction,
• the use of any tocolytic drugs during pregnancy before admission to the hospital
• circulatory system diseases (e.g. heart defects, hypertension),
• symptoms of infection
• other diseases that may increase oxidative stress

Study protocol, statistical analysis plan, informed consent form, clinical study report