[Birth weight and size: charts and equations].
OBJECTIVE
To construct new reference charts and equations for birth weight and birth size using a large and exhaustive sample of newborns. To compare this new references with previous ones.


METHODS
The study data were obtained from a single health authority (the birth registry of Yvelines, a French Territorial division of 1.4 million people) over 3 years. Multiple pregnancies were excluded. No data were excluded on the basis of abnormal biometry or birth weight. For each measurement, a least square regression model with high order polynomials was fitted to predict mean, standard deviation and therefore Z scores of birth weigh and birth size at any gestational age at birth from 25 to 42 weeks'.


RESULTS
There were 58934 and 56956 measurements included for weight and size at birth respectively. New charts and equations for Z scores calculations, adjusted for sex, are reported based on polynomial regression methods.


CONCLUSIONS
We present new French reference charts and equations for birth biometrics. Because they were derived from a very large and unselected sample, there might be more relevant to clinical practice than others and can be easily used to compute centiles and Z-scores.
Salomon
L-J
LJ
Medical Statistics Unit, London School of Hygiene and Tropical Medicine, Keppel street, London WC1E 7HT, Royaume-Uni.
Bernard
J-P
JP
de Stavola
B
B
Kenward
M
M
Ville
Y
Y
D001699:Biometry / Q000379:methods*; D001724:Birth Weight / Q000502:physiology; D005260:Female; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D012015:Reference Standards; D012016:Reference Values; D012680:Sensitivity and Specificity; D017678:Sex Distribution