Estimation of Fetal Weight during Labor: Still a Challenge.

OBJECTIVE: To evaluate the accuracy of fetal weight prediction by ultrasonography labor employing a formula including the linear measurements of femur length (FL) and mid-thigh soft-tissue thickness (STT). METHODS: We conducted a prospective study involving singleton uncomplicated term pregnancies within 48 hours of delivery. Only pregnancies with a cephalic fetus admitted in the labor ward for elective cesarean section, induction of labor or spontaneous labor were included. We excluded all non-Caucasian women, the ones previously diagnosed with gestational diabetes and the ones with evidence of ruptured membranes. Fetal weight estimates were calculated using a previously proposed formula [estimated fetal weight = 1687.47 + (54.1 x FL) + (76.68 x STT). The relationship between actual birth weight and estimated fetal weight was analyzed using Pearson's correlation. The formula's performance was assessed by calculating the signed and absolute errors. Mean weight difference and signed percentage error were calculated for birth weight divided into three subgroups: < 3000 g; 3000-4000 g; and > 4000 g. RESULTS: We included for analysis 145 cases and found a significant, yet low, linear relationship between birth weight and estimated fetal weight (p < 0.001; R2 = 0.197) with an absolute mean error of 10.6%. The lowest mean percentage error (0.3%) corresponded to the subgroup with birth weight between 3000 g and 4000 g. CONCLUSIONS: This study demonstrates a poor correlation between actual birth weight and the estimated fetal weight using a formula based on femur length and mid-thigh soft-tissue thickness, both linear parameters. Although avoidance of circumferential ultrasound measurements might prove to be beneficial, it is still yet to be found a fetal estimation formula that can be both accurate and simple to perform.

Estimation of Fetal Weight during Labor: Still a Challenge / Estimativa do peso fetal intraparto: ainda um desafio

Objective To evaluate the accuracy of fetal weight prediction by ultrasonography labor employing a formula including the linear measurements of femur length (FL) and mid-thigh soft-tissue thickness (STT). Methods We conducted a prospective study involving singleton uncomplicated term pregnancies within 48 hours of delivery. Only pregnancies with a cephalic fetus admitted in the labor ward for elective cesarean section, induction of labor or spontaneous labor were included. We excluded all non-Caucasian women, the ones previously diagnosed with gestational diabetes and the ones with evidence of ruptured membranes. Fetal weight estimates were calculated using a previously proposed formula [estimated fetal weight = [1] 1687.47 + (54.1 x FL) + (76.68 x STT). The relationship between actual birth weight and estimated fetal weight was analyzed using Pearson's correlation. The formula's performance was assessed by calculating the signed and absolute errors. Mean weight difference and signed percentage error were calculated for birth weight divided into three subgroups: < 3000 g; 3000-4000g; and > 4000 g. Results We included for analysis 145 cases and found a significant, yet low, linear relationship between birth weight and estimated fetal weight (p < 0.001; R2 = 0.197) with an absolute mean error of 10.6%. The lowest mean percentage error (0.3%) corresponded to the subgroup with birth weight between 3000 g and 4000 g. Conclusions This study demonstrates a poor correlation between actual birth weight and the estimated fetal weight using a formula based on femur length and mid-thigh soft-tissue thickness, both linear parameters. Although avoidance of circumferential ultrasound measurements might prove to be beneficial, it is still yet to be found a fetal estimation formula that can be both accurate and simple to perform.

Objetivo Avaliar a precisão da determinação ultrassonográfica da estimativa de peso fetal recorrendo apenas a parâmetros lineares (comprimento do fémur - FL - e espessura de tecido mole a meio da coxa fetal - STT), no período precedente ao parto. Métodos Realizamos umestudo prospectivo que incluiu gestações simples de termo, comfeto cefálico, nas quais o parto ocorreu nas 48h seguintes à avaliação ecográfica. A inclusão no estudo foi feita nomomento de admissão ao bloco de partos para cesariana eletiva, indução do trabalho de parto ou trabalho de parto espontâneo. Foram excluídas todas as grávidas não caucasianas, com diagnóstico de diabetes gestacional ou evidência de rotura de membranas. A estimativa de peso fetal foi calculada através de uma fórmula previamente publicada [estimativa de peso fetal = [1]1687,47 + (54,1 x FL) + (76,68 x STT). A relação entre o peso real e o peso estimado foi analisada através da correlação de Pearson. O desempenho desta fórmula foi avaliado através do cálculo da percentagem de erro absoluto e não absoluto. Os recém-nascidos foram divididos em3 grupos consoante o peso real: < 3000 g; 3000 g - 4000 g; e > 4000 g; para cada grupo foi calculada diferençamédia entre a estimativa de peso e o peso real e a percentagem de erro associada. Resultados Incluímos 145 casos no estudo, cuja estimativa de peso e peso real se correlacionaram significativamente, apesar do valor de correlação ser pouco elevado (p < 0,001; R2 = 0,197). Globalmente, a percentagem de erro absoluto foi 10,6%. A percentagem de erro mais baixa correspondeu ao grupo com peso real entre 3000 g e 4000 g. Conclusões Comeste estudo demonstramos uma correlação fraca entre o peso real e a estimativa de peso fetal ultrassonográfica, quando calculada combase numa fórmula que usa o comprimento do fémur e a espessura de tecido mole a meio da coxa fetal, ambos parâmetros lineares. Ainda que a exclusão de parâmetros circunferenciais no cálculo da estimativa de peso fetal se venha a provar benéfica, esta não parece ser uma fórmula simultaneamente simples e precisa no cálculo da estimativa de peso fetal.

Levels of agreement between clinical examination and transabdominal ultrasound evaluation of fetal head position in the second stage of labor.

AIM: To compare transvaginal digital examination performed by residents and attending physicians to transabdominal suprapubic ultrasound in the evaluation of fetal head position in the second stage of labor. METHODS: A prospective study was conducted at a tertiary center and included pregnant women at term, with normal singleton cephalic presentation fetuses. All patients had ruptured membranes and were evaluated during the second stage of labor. Fetal head position was assessed consecutively by two clinicians (one resident and one attending physician). Afterwards, transabdominal suprapubic ultrasound was performed by another observer. Examiners were blinded to each other's findings. Cohen's kappa test was used to assess the degree of agreement between the evaluation methods. RESULTS: One-hundred sixty-one women were included. Transvaginal examination was consistent with the ultrasound in 45.0% of cases (95% CI: 37-53%) when the examination was performed by residents (k = 0.349) and in 67% (95% CI: 60-74%) if the attending physician carried out the evaluation (k = 0.604). When considering only the anterior positions, the Cohen's kappa test was 0.426 and 0.709, respectively. CONCLUSION: Transabdominal suprapubic ultrasound improved the accuracy of the evaluation of fetal head position, namely when transvaginal digital examination was performed by residents. This may be important especially when instrumental deliveries are considered.