Objective: To assess the effectiveness of the newly developed individualised birthweight ratio in identifying growth retarded infants.
Design: Prospective observational study.
Setting: Obstetric unit, City Hospital Nottingham.
Subjects: Two thousand eight hundred and thirty-five women delivered between December 1991 and July 1992 and the infants of 616 of these selected by virtue of their birthweight for gestation and individualised birthweight ratio centile positions.
Main outcome measures: Skinfold thickness and ponderal index measurements, occurrence of abnormal fetal heart rate patterns, operative delivery due to fetal distress and the need for neonatal resuscitation.
Results: Using an individualised birthweight ratio less than the 10th centile as a cut-off results in 25% of those less than the 10th centile of birthweight for gestation being reclassified as normally grown. A slightly larger group are reclassified as small; significantly more of these infants have abnormal ponderal indices and skinfold thicknesses, suffer abnormal fetal heart rate patterns, operative delivery for fetal distress and need neonatal resuscitation than do those who are reclassified as normally grown.
Conclusion: The individualised birthweight ratio combines the simplicity of birthweight measurement with the accuracy of clinical measurements in the identification of the growth retarded baby.