[Estimation of small and large fetal weight at delivery from ultrasound data]. / Estimation du poids de naissance de fœtus de petit poids (≤2500g) et de gros poids (≥4000g) à partir des données échographiques.

OBJECTIVE: Birth weight (BW) prediction is crucial to assess the risk of fetal and neonatal morbidity and mortality related to growth restriction or macrosomia. Our objective here was to devise an accurate BW prediction method for small fetuses (BW ≤ 2500 g) and large fetuses (BW ≥ 4000 g), based on ultrasound data collected starting at 20 weeks' gestational age. These new models were tested on a new sample of validation consisted of 397 small fetuses and 135 large fetuses. METHODS: We included 3486 fetuses whose age and weight at birth were known and for whom standard data were available from ultrasound scans. Extrapolation to full-term of the estimated fetal weight computed using Hadlock's equation identified 212 small and 291 large fetuses. We built a new regression model for predicting the BWs of small fetuses and large fetuses. The results obtained using these models were compared to those provided by Hadlock's equation. RESULTS: Predicted BWs of small and large fetuses obtained using the regression models showed significantly less systematic bias (1.0 versus 4.9) and (-3.4 versus -7.0, respectively) and random error (10.1 versus 11.6 and 7.5 versus 8.9, respectively) than Hadlock's estimate. These results are confirmed on the sample of validation. CONCLUSIONS: Our results support the accuracy and reliability of our BW prediction models for small and large fetuses. In addition, our models provide BW estimates as early as 5 ± 1 weeks before birth.

Small and large foetuses: Identification and estimation of foetal weight at delivery from third-trimester ultrasound data.

BACKGROUND: The estimation of foetal weight (EFW) at delivery is crucial to assess the risk of foetal and neonatal morbidity and mortality, most notably when the foetus is small or large. AIM: To accurately predict the EFW at delivery of small foetuses (birth weight [BW]≤2500g) and large foetuses (BW≥4000g) identified with third-trimester ultrasound data. METHODS: We included 1309 foetuses whose age and weight at birth were known and for whom standard data were available from third-trimester ultrasound scans. Small and large foetuses were identified by extrapolation to full term of the estimated foetal weight obtained using Hadlock's equation. We built two regression models for predicting the birth weights of small and large foetuses, respectively. The results obtained with these models were compared to those obtained with Hadlock's equation. RESULTS: Third-trimester sonograms were obtained at 33.6±1.3 weeks gestational age [WGA] and birth occurred at 38.7±1.2WGA. EFW of small foetuses predicted using the regression model showed significantly less systematic bias than the Hadlock estimate (2.3% vs. 7.2%, respectively), whereas random errors were similar. EFW of large foetuses predicted using the regression model showed significantly less random error than the Hadlock estimate (6.2% vs. 10.1%, respectively), whereas systematic bias was similar. Data from an independent validation sample indicate that our regression models are accurate. CONCLUSIONS: To apply distinct models for accurately predicting the EFWs at delivery of small and large foetuses should prevent adverse events related to newborn size.

Estimation of fetal weight: accuracy of regression models versus accuracy of ultrasound data.

OBJECTIVES: To determine the respective importance of equation accuracy and variability in interexaminer measurements in estimation of fetal weight (EFW). METHODS: The study included 3 samples from three different French maternity hospitals. Sample 1 (6,508 fetuses) was used to compute a new linear regression model estimating fetal weight (FW) from ultrasound measurements. Sample 2, with 705 fetuses, was used to compare the accuracy of the new equation with Hadlock's equation. Sample 3 (1,461 fetuses) was used to assess - from our equation and from Hadlock's - the estimation errors due to the variability of ultrasound measurements recorded by 11 distinct examiners. Accuracy was determined by the signed percent difference (%Diff). Statistical analysis included the F test for correlated variances and comparisons of correlated variances. RESULTS: The random error of our model is 6.8%, significantly lower (p < 0.01) than Hadlock's which is around 7.4% (8.9% for low FW and 7.4% for high FW). The variability of ultrasound measurements among the different examiners in sample 3 generated a significant variation (p < 0.01) in the random error, ranging from 6.7 to 12.5%. This significant variation was also observed using Hadlock's equation for the same sample (from 7.2 to 12%). CONCLUSION: The accuracy of EFW depends much more on the quality of ultrasound measurements than on the choice of equation. Nevertheless, optimizing the accuracy of EFW (about 6.7-6.8%) imperatively requires standardized data collecting.

[Functional relationship between fat mass, skinfolds, under or overweight and the "ideal theoretical weight"]. / Relation fonctionnelle entre la masse grasse, les plis cutanés, le déficit ou l'excédent pondéral et le "poids théorique idéal".

Underscoring a functional relation between fat mass, skinfolds, under or overweight and the 'ideal theoretical weight', constitutes a fundamental datum in anthropology. Indeed, this relation, which differs according to age, sex, ethnic group and physical activity, provides information on the distribution of fat contained in the skinfolds, the under or overweight and the 'ideal theoretical weight'. The value of this relation lies not only in limiting the use of the corpulence index (W/H2) as an indicator of fat mass, but above all in the importance of physical activity and in the existence of a significant change in the distribution of fat according to the factors mentioned above.

[Determination of the corpulence index in newborn infants]. / Détermination d'un indice de corpulence chez le nouveau-né.

A biometric study of the somatic characteristics weight and stature carried out in 1994 on 5,751 newborn children of both sexes showed the existence of an index of corpulence of the P/T2.75 type which presents the particularity of being correlated to weight and without any link with stature, unlike Quetelet's index (P/T2) and P/T3 Roehrer's index. At fixed stature, the coefficients of the average weight variation are lower than in adults. Moreover, there is no significant difference between the average weight in boys and in girls, their fluctuations being comparable. The expression P/T2.75 allows us to compare the corpulence of newborns of both sexes having distinct weight and stature.

[Assessment and standardization of the body mass index in French males aged 18-59 years]. / Modélisation et standardisation de la corpulence chez les Français âgés de 18 à 59 ans.

This study of the corpulence of 54,360 French men aged from 18 to 59 years assessed the existence of a biological constant between height and weight. We observed a linear relation that links height to the mean weights corresponding to a fixed height. This new relationship informs us on the excess or the deficit of weight of each man and allows comparisons between body mass index in men, even if they have different heights or ages.

[Biological significance and interpretation of the corpulence index BMI (Body Mass Index)]. / Signification et interprétation biologique de l'indice de corpulence BMI (Body Mass Index).

A study of the corpulence of young French men between the age of 18 and 20 has proved the existence of a biological constant between the height and the weight, bringing a new significance to the Body Mass Index. The elaboration of a new index BMC (BMI corrected), allows us to know with precision the underweight or overweight of any individual.