Clinical significance of prenatal diagnosis of macrosomia by ultrasound

Abstract

Оbjective: Establish the diagnostic value of ultrasound examination in prenatal diagnosis of macrosomia among the women without diabetes and to determine its effect on birth outcomes. Мethods: This is a retrospective cohort study done at the Orenburg municipal perinatal center and maternity hospital № 2 since 2006 to 2012. In this study 3760 pregnant women were analyzed who delivered term, singleton, live born infants. The estimated fetal sonographic weight by the formula Hadlock’s was obtained within the last week prior to delivery. The study population was divided into 4 groups (true positive, true negative, false positive, false negative) according to the estimated fetal weight (EFW) and regarding the birth weight (BW). Receiver-operating characteristics (ROC) curves were generated to compare the prediction of macrosomia when using different observation methods. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy were calculated. The mean value of two groups were compared using two sample t test and χ² test for comparison of proportions. Results: In order to assess the accuracy of the ultrasound in prenatal diagnosis of macrosomia the study population was divided into 4 groups according to the estimated fetal weight (EFW) and regarding the birth weight (BW): true positive (n-147), false negative (n-229 ), false positive (n-353), true negative (n-3031). Results of the study showed no statistically significant differences between the birth weight and estimated fetal weifht by ultrasound alone only in the macrosomia group with true-positive results (p = 0.9). In applying the ROC (Receiver Operating Characteristic curve) performance analysis sensitivity and spesificity in the prediction of the macrosomia by ultrasound revealed the average predictive power of the method. Area under the curve (Area under ROC curve, AUC) made 0.7295 (95 % CI: 0.695-0.781), which corresponds to a predetermined average accuracy. The accuracy of macrosomia prediction by ultrasound methods was 90 %, sensitivity - 35 %, specificity - 93,5 %. Сesarian sections were performed for 40 % of the pregnant women, where fetal macrosomia was truly ruled in (true positive) and 16% of the women who delivered normal weight infants (true negative). Overestimation of fetal weight (false positive) has led to the 30 % rate of cesarean sections. Underestimation of fetal weight (false negative) has decreased to the 24% rate of cesarean sections but in this case perinatal complications have increased. Conclusion: Results showed an average accuracy in predicting macrosomia by the formula Hadlock’s. The results of the study have proved that the inappropriate prediction macrosomia of fetal weight has influence on the mode of delivery. Overestimation of fetal weight has led the proportion of cesarian sections. Underestimation of fetal macrosomia has increased perinatal complications.