Accuracy of Intrapartum Fetal Weight Estimation Using Ultrasonography and Clinical Estimation in Excessive Weight Pregnant Women
Keywords:
fetal weight, ultrasonography, clinical estimate, birth weightAbstract
Background and Objective: Predicting the expected fetal weight during pregnancy is crucial for determining the appropriate delivery techniques and the actual birth weight of the baby. Maternal weight is a significant factor that cause inaccurate assessment of intrapartum fetal weight, especially in women with excessive weight. This study aimed to investigate the accuracy of intrapartum fetal weight prediction in excessive weight pregnant women, four methods were compared namely: ultrasound, Leopold, Dare's formula and Johnson's formula.
Materials and Methods: A prospective cohort design (method-oriented study) was used to study excessive weight pregnant women (body mass index; BMI ≥ 23 Kg/m2), age 18 years or over, with a singleton pregnancy, at gestational age between 370/7 to 416/7 with vertex presentation without rupture of membrane in labor and deliver within 48 hours after admission, during July 2021 to January 2022, at Maharat Nakhon Ratchasima Hospital. The samplings were divided into 2 groups according to the weight of pregnant women on the day of delivery: 1) Overweight women (BMI = 23.0 – 27.5 Kg/ m2) 2) Obese women (BMI > 27.5 Kg/ m2). All women were measured bodyweight, height, height of fundus, abdominal circumference and per vagina examination. The intrapartum fetal wight was estimated by using the 4 methods: ultrasound, Leopold, Dare's formula, and Johnson's formula and recorded the actual birth weight of the fetus, analyzed with a mean squared error, mean difference, mean absolute relative difference and presented with modified Bland-Altman plot.
Results: From 205 excessive weight pregnant women with 63 overweight (average BMI 25.3 Kg/m2) and 142 obese (average BMI 33.7 Kg/m2), the research found that in excessive weight women the most accurate methods for predicting intrapartum fetal weight were ultrasound (mean difference (95% CI) -38.89 (-73.68, -4.10), mean absolute relative difference (MARD) 6.23 (5.56, 6.91)). While in clinical assessment, Johnson's formula method showed the highest accuracy (mean difference (95% CI) 194.20 (142.31, 246.27), MARD 10.43 (9.13, 11.72)), and followed by Leopold MARD (11.20 (9.97, 12.43) and Dare’s formula MARD 14.13 (12.38,15.87)), respectively. Moreover, when dividing women groups by weight, ultrasound was still the most accurate method for both overweight and obese women (meaning difference -67.32 (-124.08, -10.55), MARD 5.57 (4.37,6.78) and mean difference -26.82 (-70.01, 17.45), MARD (6.52 (5.70,7.34)), respectively. Lastly, for clinical fetal weight assessment, the most accurate predictive methods in overweight women were Dare's formula (mean difference 31.21 (-47.62, 110.03), MARD 8.27 (6.60, 9.95), and the most accurate predictive methods in obese women were Johnson 's formula (mean difference 237.05 (171.83, 302.27), MARD 11.08 (9.44, 12.73)).
Conclusion: Predicting the fetal weight of excessive weight pregnant women in places where equipped and personnel is available, it is recommended to make ultrasound predictions. In places without equipment or personnel, clinical estimate assessment Johnson's formula is recommended.
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