Sonographic weight estimation in fetuses with breech presentation

The birth weight of macrosomia influence the accuracy of ultrasound estimation of fetal weight at term

OBJECTIVE

To evaluate and analyze the accuracy of ultrasound estimation of the fetal weight of Macrosomia at term.

METHOD

The instruments used were α6(Aloka; Japan) color Doppler ultrasound imagers, and vinno 80 (feieno; China) with a frequency of 3.5 MHz. The formula used to calculate the estimated fetal birth weight (EFW) was that proposed by Hadlock et al. (Hadlock 2). The biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), and femur length (FL) measurements were performed strictly following the practice guidelines. Detailed measurement standards are shown in the figure and the table in the text. Macrosomia is typically defined as a birth weight above the 90th percentile for gestational age or >4000 g.Two indexes were used to calculate the error between EFW and birth weight (BW): Simple error (SE = BW - EFW); Absolute percentage error (APE, which reflects this percentage in absolute value, percentage error [PE = SE/BW] × 100). In order to better evaluate the measurement results, we made the following definitions: 1. When APE > 15%, the measurement deviation is significant. 2. The ratio of those cases with APE > 15% to the total number of cases measured by a sonographer was greater than 20%, indicating that the sonographer was prone to significant measurement deviation.

RESULT

A total of 374 cases were analyzed. The mean maternal age was 31.48 (±15.93) years. Each pregnant woman carries only one fetus. The mean gestational age at delivery was 39.93 (±0.84) weeks. There were 245 male infants (65.5%), 129 female infants (34.5%), 214 cesarean section (57.2%), and 160 vaginal delivery (42.7%). 339 cases (90.64%) were estimated to be lower than the actual BW. The estimated weight was higher than the actual weight in 35 cases, accounting for 9.36%.The APE>15% in 56 cases, accounting for 14.97%. The accuracy of estimated fetal weight was closely related to the BW of the fetus and had no significant correlation with the seniority of the physician, the gender of the fetus, and the fetal position.

CONCLUSION

Studies on macrosomia have shown that the BW of macrosomia tends to be underestimated, which is also reflected in the results of this study. The accuracy of estimated fetal weight still needs to be improved. Our study found that the accuracy of estimated fetal weight was closely related to the BW of the fetus and had no significant correlation with the seniority of the physician, the gender of the fetus, and the fetal position. The correlation between the section and calculation formula on the measurement accuracy needs to be studied. Through systematic data analysis, we can find the doctors whose measurements are relatively inaccurate in our department and carry out targeted quality control to improve the measurement accuracy.

Differences in Biometric Fetal Weight Estimation Accuracy and Doppler Examination Results in Uncomplicated Term Singleton Pregnancies between Vertex and Breech Presentation

Doppler examination of the umbilical artery and the fetal middle cerebral artery is evaluated predominantly in pregnancies with fetuses in cephalic presentation and never has been elucidated in breech presentation. Evidence on the accuracy of fetal weight estimation in dependence of the fetal presentation is controversial. Nevertheless, clinical decisions including recommendations for a cesarean section or labor induction based on these examinations are applied to pregnancies with fetuses in breech presentation. The objective of this study was to investigate the influence of the fetal presentation on fetal weight estimation accuracy, umbilical artery and middle cerebral artery resistance indices (RI) in a prospective case control study. Ultrasound examinations in 305 uncomplicated term pregnancies (153 vertex presentations, 152 breech) were investigated. Non-parametric variables were compared using Pearson’s chi² test and Wilcoxon chi² test, depending on variable scaling. Fetal weight estimation accuracy was not significantly different between vertex presentation group (VP) (6.97%) and breech presentation group (BP) (7.96%, p = 0.099). Fetal head circumference measurements were significantly larger in BP (350 mm vs. 341 mm in VB, p > 0.0001) while abdominal circumferences were significantly smaller (VP: 338 mm, BP: 331 mm, p = 0.0039) and weight estimation was not significantly different. Umbilical artery RIs were not significantly different between VP (54.5) and BP (55.3, p = 0.354). Fetal middle cerebral artery RIs also showed no significant differences (VP: 71.2, BP: 70.7, p = 0.335). Our study shows that fetal Doppler (RI) and weight estimation ultrasound originally calibrated in cephalic pregnancies are applicable to pregnancies with fetuses in breech presentation.

Observer Influence with Other Variables on the Accuracy of Ultrasound Estimation of Fetal Weight at Term

Background and Objectives: The accuracy with which the estimation of fetal weight (EFW) at term is determined is useful in order to address obstetric complications, since it is a parameter that represents an important prognostic factor for perinatal and maternal morbidity and mortality. The aim of this study was to determine the role of the experienced observers with other variables that could influence the accuracy of the ultrasound used to calculate EFW at term, carried out within a period of seven days prior to delivery, in order to assess interobserver variability. Materials and Methods: A cross-sectional study was performed including 1144 pregnancies at term. The validity of the ultrasound used to calculate EFW at term was analyzed using simple error, absolute error, percentage error and absolute percentage error, as well as the percentage of predictions with an error less than 10 and 15% in relation to maternal, obstetric and ultrasound variables. Results: Valid predictions with an error less than 10 and 15% were 74.7 and 89.7% respectively, with such precision decreasing according to the observer as well as in extreme fetal weights. The remaining variables were not significant in ultrasound EFW at term. The simple error, absolute error, percentage error and absolute percentage error were greater in cases of extreme fetal weights, with a tendency to overestimate the low weights and underestimate the high weights. Conclusions: The accuracy of EFW with ultrasound carried out within seven days prior to birth is not affected by maternal or obstetric variables, or by the time interval between the ultrasound and delivery. However, accuracy was reduced by the observers and in extreme fetal weights.

Accuracy of sonographic fetal weight estimation in full-term singleton pregnant women

Objectives

To investigate the factors which might influence the sonographic fetal weight estimation (SFWE) accuracy.

Methods

This prospective study was conducted among 949 singleton term pregnant women who delivered at a tertiary center, from January 2017 to December 2017. All participants' maternal (i.e. parity, age, body mass index and gestational weight gain during pregnancy), fetal sonographic (i.e. fetal presentation, amniotic fluid index, localization of placenta and estimated fetal weight) and neonatal (birth weight and gender) characteristics were recorded. A p<0.05 was considered significant.

Results

The mean absolute percent error (APE) values of SFWE was 8.2±6.5 percent, and overall failure ratio (APE >10%) was 33%. In failure group, primiparous woman and cephalic presentation fetus were significantly more common compared to accuracy group (55.9% vs.44.8%; p=0.001 and 98% vs. 95.2%; p=0.03, respectively). In contrast, the mean neonatal birth weight (NBW) value was significantly lower in failure group compared to success group (3250±565 gr vs. 3404±410 gr; p=0.001). The correlation between SFWE and NBW was linear, however negative, and significant (p=0.001). Logistic regression analysis revealed that primiparous woman, cephalic presentation fetus and <3300 gr NBW were independent risk factors for the SFWE failure (relative risks were 1.6, 2.8 and 2.4 respectively, p<0.05).

Conclusion

SFWE has a high correlation with NBW, however it's accuracy is still unsatisfactory, and depend on many unpredictable and inconsistent factors.

Sonographic prediction of small and large for gestational age in breech-presenting fetuses

Introduction:

To evaluate various sonographic estimated fetal weight (sEFW) formulas’ accuracy for small- and large-for-gestational age (SGA/LGA) prediction in breech-presenting fetuses.

Materials and methods:

A retrospective analysis of all ultrasound-based fetal biometrical measurements performed within 3 days of delivery in term pregnancies, in one medical center (2007–2014). Overall, 274 breech-presenting fetuses (study group) were compared to 274 vertex-presenting fetuses (control group) matched by gender, gestational age and birth weight. sEFW was calculated by six previously published formulas. Accuracy was compared utilizing systematic error and random error for every formula. Prediction precision of SGA and LGA was evaluated by calculating each formula’s sensitivity, specificity, +/− predictive value, and the area under the receiver-operating characteristic (ROC) curve (AUC).

Results:

Systematic error and random error varied greatly between formulas, ranging from −7.4% to 3.1%, 7.3% to 8.3% for the vertex-presenting fetuses and −8.9% to 1.9%, 7.9% to 8.6% for the breech-presenting fetuses, respectively. There was no statistical difference in small- or large-for-gestational age prediction parameters between the groups. The highest sensitivity and specificity for prediction was achieved by same formula regardless of presentation.

Conclusion:

In our cohort, overall accuracy was slightly superior among vertex-presenting fetuses without difference in prediction accuracy for small- and large-for-gestational age neonates.

Accuracy of sonographic fetal weight estimation prior to delivery in a Chinese han population

OBJECTIVE

To compare the sonographic-estimated fetal weights (EFW) calculated with the Hadlock formula and with the Woo formula in a group of Chinese pregnant women.

METHODS

We prospectively recruited term pregnancies for sonographic biometric examination. EFWs were calculated according to two formulas and compared with the corresponding birth weight (BW). We also assessed the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of EFW for the diagnosis of small-for-gestational age (SGA) and large-for-gestational age (LGA) neonates.

RESULTS

A total of 374 subjects who delivered within 7 days after the sonographic examinations was recruited. Using the Hadlock formula, the median absolute difference between EFW and BW was 182 g (15-308 g) and the median percentage difference was 5.3% (0.5-9.1%), whereas it was 230 g (62-367) and 7.1% (2.1-10.4%) for the Woo formula (p < 0.001). Several factors, namely the fetal presentation, gender, and high amniotic quantity, showed no evident impact on this predictive difference. Among the 175 women who delivered within 2 days after ultrasound, the sensitivity and specificity of Hadlock EFW were 100% and 97.1% for the detection of SGA and 48.1% and 97.3% for the detection of LGA, respectively. The PPV and NPV were 44.4% and 100.0% for the detection of SGA and 76.5% and 91.1% for the detection of LGA, respectively.

CONCLUSIONS

EFWs calculated using the Hadlock formula for our research subjects were as accurate as those reported for other populations. The predictive performance showed a high NPV for the diagnosis of SGA and a relatively acceptable PPV for the diagnosis of LGA. © 2017 Wiley Periodicals, Inc. J Clin Ultrasound 45:465-471, 2017.

Effect of fetal presentation on sonographic estimation of fetal weight according to different formulas

OBJECTIVE

To compare the accuracy of various sonographic estimation of fetal weight (sEFW) formulas for breech-presenting fetuses.

METHODS

A retrospective analysis of sEFW performed within 3 days of delivery in a tertiary medical center in Israel between July 2007 and December 2014 was conducted. Breech-presenting singleton fetuses were matched by sex and birth weight to vertex-presenting fetuses. sEFW was calculated using 21 formulas. Systematic and random errors, proportion of estimates (POE) within 10% of actual birth weight, and reliability analysis were used to compare sonographic accuracy. The best performing formula was determined by Euclidean distance.

RESULTS

Both groups contained 274 fetuses. Systematic error was lower for breech fetuses when compared with control fetuses in 17 of 21 formulas; there was no significant difference in random error between the breech and vertex groups. For vertex fetuses, Euclidean distance was smaller in 17 of 21 formulas, and POE within 10% of birth weight was higher in most formulas. Cronbach α value was higher for vertex fetuses than for breech fetuses in all formulas. The formulas of Combs et al. and Hadlock et al. were highest ranking for breech-presenting fetuses.

CONCLUSION

sEFW might be more accurate for vertex than for breech fetuses.

Predicting birth weight with conditionally linear transformation models

Low and high birth weight (BW) are important risk factors for neonatal morbidity and mortality. Gynecologists must therefore accurately predict BW before delivery. Most prediction formulas for BW are based on prenatal ultrasound measurements carried out within one week prior to birth. Although successfully used in clinical practice, these formulas focus on point predictions of BW but do not systematically quantify uncertainty of the predictions, i.e. they result in estimates of the conditional mean of BW but do not deliver prediction intervals. To overcome this problem, we introduce conditionally linear transformation models (CLTMs) to predict BW. Instead of focusing only on the conditional mean, CLTMs model the whole conditional distribution function of BW given prenatal ultrasound parameters. Consequently, the CLTM approach delivers both point predictions of BW and fetus-specific prediction intervals. Prediction intervals constitute an easy-to-interpret measure of prediction accuracy and allow identification of fetuses subject to high prediction uncertainty. Using a data set of 8712 deliveries at the Perinatal Centre at the University Clinic Erlangen (Germany), we analyzed variants of CLTMs and compared them to standard linear regression estimation techniques used in the past and to quantile regression approaches. The best-performing CLTM variant was competitive with quantile regression and linear regression approaches in terms of conditional coverage and average length of the prediction intervals. We propose that CLTMs be used because they are able to account for possible heteroscedasticity, kurtosis, and skewness of the distribution of BWs.

Vaginal delivery or cesarean section at term breech delivery--chance or risk?

AIM

The aim of the study was to examine maternal age, parity, and estimated neonatal birth weight (BW) depending on the mode of a full-term breech presentation (BP) birth delivery and neonatal outcomes.

MATERIAL AND METHODS

One hundred and forty-six singleton term breech presentation pregnancies were included in a retrospective study conducted at the Department of Gynecology/Obstetrics, Clinical Center of Serbia in Belgrade in 2013. Statistical analysis: Student's-t test, χ(2) likelihood ratio, and the Fisher's exact test. The level of statistical significance was set at p <0.05.

RESULTS

An ECS was the most common mode of delivery in (81.2%) nulliparous older than 35 years and most of the neonates (66.67%) with an estimated birth weight (BW) above 3500 grams were delivered by elective cesarean section (ECS). Perinatal asphyxia remained increased in the successful vaginal delivery (SVD) group (23.8%) compared with the urgent CS (UCS) group (13.3%) (p = 0.035). Birth asphyxia was the most common in neonates were delivered by SVD (23.8%). There were no cases of perinatal deaths.

CONCLUSION

ECS remained the recommended mode of breech term delivery in nulliparous women older than 35 years, as well as in neonates with an estimated BW above 3500 grams.

Sonographic fetal weight estimation - is there more to it than just fetal measurements?

OBJECTIVES

The primary aim of this study was to evaluate the effects of different maternal, fetal, and examiner related factors on the accuracy of sonographic fetal weight estimation (SFWE).

METHODS

A retrospective cohort study analyzing 9064 SFWEs performed within 1 week prior to delivery, including singleton pregnancies with a gestational age of 37 to 42 weeks, was recorded at one medical center from January 2004 to September 2011. Predicted birth weights were calculated according to models by Sabbagha et al., Hadlock et al., and Combs et al. and were compared with the actual birth weight. Effects of different factors on SFWE accuracy were assessed. The systematic error, random error, and mean absolute percentage error were used as measures of accuracy.

RESULTS

High maternal weight, height, body mass index, multiparity, older maternal age, diabetes, and fetal male sex were associated with underestimation of SFWE (P < 0.05). Fetal presentation and the sonographer's experience influenced SFWE differently using various models. The amniotic fluid index did have a significant effect on SFWE. Overall, more than 90% of the systematic errors were unaccounted for in the factors we assessed.

CONCLUSIONS

Many maternal and fetal factors significantly influence the SFWE; nevertheless, most errors are probably due to inherent problems in SFWE formulas.