Current clinical protocols for blood sampling and analyses in extremely preterm infants rely on an infrastructure adapted to and developed for adult medicine. Excessive blood sampling volumes and the resulting loss of fetal blood components are related to neonatal morbidity. This randomised trial aims to provide evidence that preservation of blood using micro-methods results in decreased morbidity and increased quality of life in extremely preterm infants.

Extremely preterm (EPT) infants are subjected to a sample-related withdrawal of whole blood of 50 % of total blood volume during the first 2 postnatal weeks and a transfused volume of 100 % of total blood volume with donor blood during the corresponding time period. The resulting decrease in the proportion of fetal hemoglobin is strongly associated with morbidity outcome, especially broncho-pulmonary dysplasia (BPD), in the EPT infant.

This randomized trial evaluates if a reduction in sample-related blood volume loss by 50% during the first two postnatal weeks leads to a reduced rate of BPD in EPT infants. Half of the included infants will be subjected to clinical blood sampling using micromethods during the first two postnatal weeks whereas blood sampling in the other half of infants will be performed using standard clinical methods.

Inclusion Criteria:

• gestational age < 27 weeks at birth

Exclusion Criteria:

• major malformation

Prevalence and severity of BPD at 36 weeks post-menstrual age is determined by the oxygen challenge test performed by a trained respiratory nurse blinded to treatment at each study site.