Rapid estimation of birth weights: ask the mother

Analysis of the effectiveness of ultrasound and clinical examination methods in fetal weight estimation for term pregnancies

Objective:

To compare the accuracy of clinical and ultrasonographic (USG) estimation of fetal weight in non-complicated, term pregnancies.

Materials and Methods:

Two hundred term pregnant women were included in the study. We used three formulae for the estimation of fetal weight at term; the Hadlock formula for the USG method, and two different formulas for clinical methods, maternal symphysis-fundal height and abdominal circumference at the level of umbilicus. Accuracy was determined by mean percentage error, mean absolute percentage error and proportion of estimates within 10% of actual birth weight (birth weight ±10%). Patients were divided into two groups according to actual birth weight, the normal birth weight group (2500-3999 g) and high birth weight group (≥4000 g).

Results:

All three methods statistically overestimated birth weight for the high and normal birth weight groups (p<0.001, p=1.000, p=0.233) (p=0.037, p<0.001, and p<0.001). For both groups, the mean absolute percentage errors of USG were smaller than for the other two clinical methods and the number of estimates were within 10% of actual birth weight for USG was greater than for the clinical methods; the differences were statistically significant (p<0.001). No statistically significant difference of accuracy was observed for all three methods for the high birth weight group (p=0.365, p=0.768, and p=0.540). However, USG systematically underestimated birth weight in this group.

Conclusion:

For estimation of fetal birth weight in term pregnancies, ultrasonography is better than clinical methods. In the suspicion of macrosomia, it must be remembered that no method is better than any other. In addition, if ultrasonography is used, careful management is recommended because ultrasonography overestimates in this group.