• Impact factor;
  • Neonatology;
  • Publication bias;
  • Randomized clinical trial


Aim:  To test the hypotheses that published randomized clinical trials (RCTs) in neonatology with negative results (NR) are more likely to be published in journals with lower impact factor (IF) than those with positive results (PR); that there is an increase in the number of yearly published RCTs; that studies with large sample sizes are likely to be published in journals with higher IF.

Methods:  We used all English-written RCTs registered in MEDLINE between 1/1/2001–31/12/2010 in the field of neonatology. Each RCT was classified as having a PR or NR. IF of each journal was determined for the year of publication.

Results:  We identified 329 RCTs. Yearly number of RCTs varied between 19 and 46, with no significant consistent linear increase over the years. There was no significant change over the years in average IF or in average patient size. IF and sample size of the studies were not significantly higher in studies with PR than in studies with NR.

Conclusion:  The number of RCTs per year in the field of neonatology has stabilized in the past 10 years, and RCTs with positive or negative results are published in journals of similar IF.