Validity of sonographic formulas for estimating fetal weight below 1,250 g: a series of 119 cases.
OBJECTIVE
The aim of this study was to determine the accuracy of sonographic methods for estimating fetal weight < 1,250 g on the basis of ten published formulas falling into two principal categories: general formulas applied to all fetuses, and formulas specifically developed for very-low-weight fetuses.


METHODS
Recent biometric data (obtained less than 7 days before birth) on 119 fetuses weighing < 1,250 g were used retrospectively. Estimated fetal weights derived from ten published formulas were compared to actual weights. For each equation, the errors in predicting fetal weight were used to calculate mean percentage error and standard deviation of the mean error. The t test was used to determine whether the mean errors were significatively different from zero. The F test was used to determine if there were significant differences in the standard deviation of the mean errors.


RESULTS
The mean birth weight of infants was 956 +/- (SD) 183 g at a gestational age of 29 +/- (SD) 2.3 weeks. The best three formulas were the Hadlock, Sabbagha and Mielke which generated a mean error of -0.25, 2.81 and 0.29 not statistically different from zero with standard deviations of 13.02, 9.14 and 11.96, which were not statistically different.


CONCLUSIONS
In our population of very-low-birth-weight infants, the use of specific formulas targeted to those fetuses does not provide a more accurate estimation of fetal weight.
Jouannic
J M
JM
Maternité Port-Royal, Hôpital Cochin, Paris, France. jouannic@nck.ap-hop-paris.fr
Grangé
G
G
Goffinet
F
F
Benachi
A
A
Carbrol
D
D
D005260:Female; D020567:Fetal Weight; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D019102:Infant, Very Low Birth Weight; D011247:Pregnancy; D015203:Reproducibility of Results; D016216:Ultrasonography, Prenatal / Q000379:methods* / Q000592:standards*