Individual growth curve standards in triplets: prediction of third-trimester growth and birth characteristics

We investigated the ability of Rossavik growth models, determined from measurements obtained before 24 weeks (head circumference [HC], abdominal circumference [AC], femur diaphysis length, and estimated fetal weight [EFW]) or 25 weeks (thigh circumference), to predict third-trimester growth and birth characteristics in normally growing triplets. Comparisons of coefficient c values for six anatomical measurements indicated no statistically significant differences in the second-trimester growth of triplets, twins, and singletons. Third-trimester triplet values for HC, AC, and femur diaphysis length were predicted with an accuracy of +/- 6-8%. For thigh circumference and EFW, the comparable values were +/- 17 and +/- 15%, respectively. The HC at birth was predicted without bias; the random error was approximately -27 to 9.0%. Weight, AC, and thigh circumference were systematically overestimated (16.5, 20.9, and 16.3%, respectively). After correction for systematic errors, these characteristics could be predicted with random errors of -13.0 to 9.5% (weight), -12.0 to 2.8% (AC), and -16.7 to 11.3% (thigh circumference). Growth Potential Realization Index values had means of approximately 100% and ranges from 90-121%. The mean triplet value of the Neonatal Growth Assessment Score was 13.6, ranging from 2.8-26.5. These results are similar to those for singletons and twins and indicate that individual assessment of growth in triplets can be performed with the same methods used for both singletons and twins.