Birth weight percentiles of premature infants needs to be updated

OBJECTIVE: To analyse whether the conventional so-called Kloosterman charts for birthweight of preterm infants based on data from 1931-1965 are still valid. DESIGN: Descriptive investigation. LOCATION: The Netherlands. METHOD: Data were obtained from the 'project of the premature and small for gestational age' (POPS) survey in 1983. The population consisted of 855 Caucasian infants born after a pregnancy of 24-31 weeks. RESULTS: In nearly all gestational age categories the percentages of small-for-gestational age infants were higher than the 10% they should have been by definition; the percentages of large-for-gestational age infants were much lower than 10%. After exclusion of elective births the percentages remained different. CONCLUSION: These shifts in the birthweight distribution are probably the result of changes in obstetrics. The birthweight percentiles for preterm births will have to be updated.