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The main objective of the review was to assess the short- and long-term effects of placental transfusion according to the timing of cord clamping and/or the position of the neonate relative to the level of the placenta and/or the milking of the umbilical cord in infants born at less than 37 completed weeks' gestation. Delayed cord clamping was defined as cord clamping between 30–120 seconds after birth.

Of the 16 trials identified, the authors selected seven and requested additional information for three. Blood transfusion for anemia and the risk of intraventricular haemorrhage were the two variables for which delayed cord clamping was beneficial. For most other outcomes there were insufficient data to evaluate the effects reliably. The trial by Mercer et al. (1) is listed as 'ongoing' but this trial has recently been published and should be eligible for inclusion in this review.

The authors correctly identify several inconsistencies within the evaluated trials. These mainly relate to the use of different definitions of terms (“intervention”, “immediate cord clamping” and “delayed cord clamping”) and to the outcome variables included. Most trials did not state whether the timing of cord clamping was measured and whether any guidelines were followed with respect to the indication of blood transfusion in neonates; the latter makes it difficult to know whether the indication of blood transfusion in neonate was dealt with in a similar manner in all the trials. Finally, the trials did not define many of the variables included. These limiting factors affect the reliability of the results.

Although the authors of the review had defined stratification categories, taking into account possible confounding factors, this was not possible to implement the stratification due to the limited number of papers and their marked heterogeneity. Also, not all the trials considered all the outcome variables. Consequently, the review had to rely on a limited number of trials that included the different outcome variables. Therefore, even though the conclusions of the review do not reliably indicate any benefits of delayed cord clamping, it would be plausible to assert that delayed cord clamping would not result in any conditions that become a risk for infants born at less than 37 completed weeks'.

Another aspect of the trials that needs to be emphasized is that not all included trials achieved their estimated required sample size. Considering the main outcomes—need of blood transfusion and intraventricular hemorrhage—the sample size obtained after combining the trials was enough in the first case (n=111), taking into account 52% and 55% frequencies of need of blood transfusion in each arm of the trial. In the case of intraventricular hemorrhage, the sample size obtained in the review (n=225) was close to that required.

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