Although thrombocytopenia has been reported as a risk factor for patent ductus arterioses, there is lack of data on the function of platelets in ductal closure. Information on functions of platelets in ductal closure may change the known model for ductus arterioses and may affect the treatment modalities.

Patent ductus arterioses is a common problem which involves both pulmonary and cardiac outcomes in preterm infants. Although thrombocytopenia has been reported as a risk factor for patent ductus arterioses, there is lack of data on the function of platelets in ductal closure.

The investigators aim to investigate the relation between thrombocytopenia and platelet functions in pathogenesis of spontaneous ductal closure. The investigators hypothesize that Information on functions of platelets in ductal closure may change the known model for ductus arterioses and may affect the treatment modalities.

Inclusion Criteria:

• gestational age lower than 30 weeks and birth weight lower than 1500 g
• obtained informed consent

Exclusion Criteria:

• any received medical treatment in first 2 days of life
• death in first 2 days
• patients who received any thrombocyte or fresh frozen plasma suspensions
• any known genetic thrombocyte disorder in the family

preterm infants with gestational age below 30 weeks and birth weght lower than 1500 g