Objective: To construct new Dutch reference curves for birthweight by parity, sex and ethnic background.
Design: Retrospective nationwide study.
Material and methods: Reference curves for birthweight were constructed using the LMS model and were based on 176,000 singleton births in the Netherlands in the year 2001 (approximately 95% of all births in that year).
Results: Separate birthweight curves were constructed for male and female babies born from primiparous and multiparous women from 25 to 43 weeks gestational age. The reference curves are similar to the Swedish references. Birthweight at early gestation was lower than in the previous Dutch reference curves and higher from term onwards. Infants of Hindustani women had a significantly lower birthweight, so that a separate reference curve was constructed.
Conclusion: The new Dutch reference curves show a different pattern than the Dutch reference curves collected more than 50 years ago, reflecting changes in prenatal conditions and care.