Assessment of fetal weight based on ultrasonic femur length after the second trimester

Prediction of Neonatal Growth Restriction in Fetuses With Gastroschisis by Early Third Trimester Ultrasonography Utilizing Contemporary Birth Weight Percentiles

OBJECTIVE

To identify the estimated fetal weight (EFW) formula and threshold for the optimal prediction of fetal growth restriction (FGR) at 26-34 weeks' in fetuses with gastroschisis.

METHODS

Late second and third trimester ultrasound data were used to calculate the EFW utilizing eight different formulas: Hadlock I-IV, Honarvar, Shepard, Siemer, and Warsof. EFW and birth weight percentiles were assigned from US population growth curves. FGR and small for gestational age (SGA) were defined as EFW and birth weight less than the tenth percentile for gestational age; Receiver operating characteristic (ROC) curves were used to compare formula performance for FGR diagnosis at 26-34 weeks' to identify an SGA birth weight.

RESULTS

There were 170 newborns with gastroschisis; 46 (27%) were SGA. The mean gestational age at the time of ultrasound was 30.8 ± 1.7 weeks. The mean gestational age at birth was 36.3 ± 1.7 weeks. ROC curve analysis found the Hadlock III formula had the largest area under the curve (AUC) of 0.813 closely followed by Hadlock IV (AUC = 0.811) and Hadlock II (AUC = 0.808) for diagnosis of FGR correlating to neonatal SGA diagnosis. Hadlock II, Hadlock III, and Hadlock IV had the highest diagnostic accuracies when compared to the other EFW formulas.

CONCLUSIONS

The Hadlock II, Hadlock III, and Hadlock IV formulas have comparable predictive performance in the optimal identification of FGR in fetuses with gastroschisis at 26-34 weeks'. A threshold of an EFW less than the 25.2th percentile is suggested.

Accuracy of Ultrasound to Predict Neonatal Birth Weight Among Fetuses With Gastroschisis: Impact on Timing of Delivery

OBJECTIVES

To determine the accuracy of ultrasound estimation of fetal weight among fetuses with gastroschisis and how the diagnosis of fetal growth restriction (FGR) affects the timing of delivery.

METHODS

This was a retrospective cohort study including all fetuses with a diagnosis of gastroschisis at our institution from November 2012 through October 2017. We excluded multiple gestations, pregnancies with major structural or chromosomal abnormalities, and those for which prenatal and postnatal follow-up were unavailable. Performance characteristics of ultrasound to predict being small for gestational age (SGA) were calculated for the first and last ultrasound estimations of fetal weight.

RESULTS

Our cohort included 75 cases of gastroschisis. At the initial ultrasound estimation, 15 of 58 (25.9%) fetuses met criteria for FGR; 48 of 70 (68.6%) met criteria at the time of the last ultrasound estimation (median, 34.7 weeks). Cesarean delivery was performed for 37 of 75 (49.3%), with FGR and concern for fetal distress as the indication for delivery in 17 of 37 (45.9%). Only 6 of 17 (35.3%) of the neonates born by cesarean delivery for an indication of FGR and fetal distress were SGA. The initial ultrasound designation of FGR corresponded to SGA at birth in 8 of 15 (53.3%), whereas the last ultrasound estimation corresponded to SGA in 17 of 48 (35.4%). The initial ultrasound estimation agreed with the last ultrasound estimation before delivery with the diagnosis of FGR in 13 of 15 (86.7%).

CONCLUSIONS

Ultrasound in the third trimester was sensitive but had a low positive predictive value and low accuracy for the diagnosis of SGA at birth for fetuses with gastroschisis. A large proportion of fetuses were born by cesarean delivery with indications related to FGR or fetal concerns.

Relationship between fetal biometric assessment by ultrasonography and neonatal lamb vitality, birth weight and growth

Ultrasonographic examination of pregnant ewes can enable the identification of perinatal abnormalities and establish prenatal assistance responsible for minimizing morbidity and perinatal mortality. Therefore, we aimed to evaluate the feasibility of a fetal biometric analysis by ultrasonography to predict neonatal vitality and lamb growth during the first month of life. A longitudinal study was conducted with 13 healthy ewes, subjected to ultrasonographic examination every 15 days from 60^th day of pregnancy until lambing, evaluating thoracic diameter, abdominal diameter, biparietal diameter, humerus, femur and placentome length. At birth, 22 lambs were assessed through Apgar score at 5 minutes and after 1 hour. Measurement of body weight was also carried out immediately at birth and weekly during 30 days after birth. Thoracic diameter showed a significant increase between 91-105 days and 121-135 days. Conversely, abdominal diameter had a progressive growth until 106-120 days, and then, a steady development was observed. Biparietal diameter showed progressive growth only towards days 91 and 105. For the humerus length, we verified a significant increase between 106-120 days and 121-135 days, remaining unaltered onwards; while femur length continued to grow until lambing. The linear regression analysis between birth weight and biparietal diameter at 60-75 days was high (R²=0.96; P<0.0001; coefficient of variability of 3.3%). In conclusion, ultrasonographic analysis of fetal biparietal diameter at mid-pregnancy can be used as a predictor of lamb weight at birth. Moreover, assessment of femur length at final pregnancy can be employed for fetal and neonatal development estimation.

Fetal growth standards in gastroschisis: Reference values for ultrasound measurements

OBJECTIVES

The objectives of this study were to create growth curves based on ultrasonography biometric parameters of fetuses with gastroschisis, comparing them with normal growth standards, and to analyze umbilical artery (UA) Doppler velocimetry patterns.

METHODS

A cohort study of 72 fetuses with gastroschisis, at gestational ages between 14 and 39 weeks was designed. Mean and standard deviation were calculated, with the 5th, 10th, 50th, 90th, and 95th centiles being established for biometric parameters according to gestational age. Curves were obtained, comparing with normal reference via the Mann-Whitney test. UA Doppler velocimetry patterns were obtained.

RESULTS

A total of 434 examinations were performed, and centiles were established for biparietal diameter, head circumference, abdominal circumference, femur length, and estimated fetal weight. A significant difference was observed between the gastroschisis measurements when compared to control, with all curves shifted downwards. Abdominal circumference was the parameter presenting the largest difference. Estimated fetal weight was also lower, with mean difference of 256.3 ± 166.8 g for the 50th centile (P < .0001). UA Doppler velocimetry was normal in 97.5%.

CONCLUSIONS

Fetuses with gastroschisis show symmetrical growth deficits in the second and third trimesters, with normal UA Doppler velocimetry. These results reinforce the hypothesis that they are constitutionally smaller, yet not restricted because of placental insufficiency.

Ultrasonographic estimation of fetal weight: development of new model and assessment of performance of previous models

OBJECTIVES

To develop a new formula for ultrasonographic estimation of fetal weight and evaluate the accuracy of this and all previous formulae in the prediction of birth weight.

METHODS

The study population consisted of 5163 singleton pregnancies with fetal biometry at 22-43 weeks' gestation and live birth of a phenotypically normal neonate within 2 days of the ultrasound examination. Multivariable fractional polynomial analysis was used to determine the combination of variables that provided the best-fitting models for estimated fetal weight (EFW). A systematic review was also carried out of articles reporting formulae for EFW and comparing EFW to actual birth weight. The accuracy of each model for EFW was assessed by comparing mean percentage error, absolute mean error (AE), proportion of pregnancies with AE ≤ 10% and Euclidean distance.

RESULTS

The most accurate models, with the lowest Euclidean distance and highest proportion of AE ≤ 10%, were provided by the formulae incorporating ≥ 3 rather than < 3 biometrical measurements. The systematic review identified 45 studies describing a total of 70 models for EFW by various combinations of measurements of fetal head circumference (HC), biparietal diameter, femur length (FL) and abdominal circumference (AC). The most accurate model with the lowest Euclidean distance and highest proportion of AE ≤ 10% was provided by the formula of Hadlock et al., published in 1985, which incorporated measurements of HC, AC and FL; there was a highly significant linear association between EFW and birth weight (r = 0.959; P < 0.0001), and EFW was within 10% of birth weight in 80% of cases. The performance of the best model developed in this study, utilizing HC, AC and FL, was very similar to that of Hadlock et al. CONCLUSION: Despite many efforts to develop new models for EFW, the one reported in 1985 by Hadlock et al., from measurements of HC, AC and FL, provides the most accurate prediction of birth weight and can be used for assessment of all babies, including those suspected to be either small or large. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.

Predicting birth weight in fetuses with gastroschisis

OBJECTIVE

To determine the accuracy of commonly utilized ultrasound formulas for estimating birth weight (BW) in fetuses with gastroschisis.

STUDY DESIGN

A retrospective review was conducted of all inborn pregnancies with gastroschisis within the five institutions of the University of California Fetal Consortium (UCfC) between 2007 and 2012. Infants delivered at ⩾28 weeks who had an ultrasound within 21 days before delivery were included. Prediction of BW was evaluated for each of the five ultrasound formulas: Hadlock 1 (abdominal circumference (AC), biparietal diameter (BPD), femur length (FL) and head circumference (HC)) and Hadlock 2 (AC, BPD and FL), Shepard (AC and BPD), Honarvar (FL) and Siemer (BPD, occipitofrontal diameter (OFD), and FL) using Pearson's correlation, mean difference and percent error and Bland-Altman analysis. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) for the ultrasound diagnosis of intrauterine growth restriction (IUGR) were assessed.

RESULTS

We identified 191 neonates born with gastroschisis within the UCfC, with 111 neonates meeting the inclusion criteria. The mean gestational age at delivery was 36.3±1.7 weeks and the mean BW was 2448±460 g. Hadlock (1) formula was found to have the best correlation (r=0.81), the lowest mean difference (8±306 g) and the lowest mean percent error (1.4±13%). The Honarvar and Siemer formulas performed significantly worse when compared with Hadlock 1, with a 13.7% (P<0.001) and 3.9% (P=0.03) difference, respectively, between estimated and actual BW. This was supported by Bland-Altman plots. For Hadlock 1 and 2, sensitivity was 80% with a NPV of 91%.

CONCLUSION

The widely used Hadlock (1) and (2) formulas provided the best estimated BW in infants with gastroschisis despite its inclusion of abdominal circumference. Furthermore, this formula performs well with diagnosis of IUGR.

Ultrasound estimation of birth weight in twin pregnancy: comparison of biometry algorithms in the STORK multiple pregnancy cohort

OBJECTIVES

The aims of this study were first, to ascertain the accuracy of formulae for ultrasonographic birth-weight estimation in twin compared with singleton pregnancies and second, to assess the accuracy of sonographic examination in the prediction of birth-weight discordance in twin pregnancies.

METHODS

This was a retrospective cohort study including both singleton and twin pregnancies. Routine biometry was recorded and estimated fetal weight (EFW) calculated using 33 different formulae. Only pregnancies that delivered within 48 h of the ultrasound scan were included (4280 singleton and 586 twin fetuses). Differences between the EFW and actual birth weight (ABW) were assessed by percentage error, accuracy in predictions within ± 10% and ± 15% of error and use of the Bland-Altman method. The accuracy of prediction of the different cut-offs of birth-weight discordance in twin pregnancies was also assessed using the area under the receiver-operating characteristics curve (AUC).

RESULTS

The overall mean absolute percentage error was ≤ 10% for 25 formulae in singleton pregnancies compared with three formulae in twin pregnancies. The overall predictions within ± 10% and ± 15% of the ABW were 62.2% and 81.5% in singleton and 49.7% and 68.5% in twin pregnancies, respectively. When t e formulae were categorized according to the biometric parameters included, those based on a combination of head, abdomen and femur measurements showed the lowest mean absolute percentage error, in both singleton and twin pregnancies. The predictive accuracy for 25% birth-weight discordance using the Hadlock 2 formula, as assessed by the AUC, was 0.87.

CONCLUSIONS

Ultrasound estimation of birth weight is less accurate in twin than in singleton pregnancies. Formulae that include a combination of head, abdomen and femur measurements perform best in both singleton and twin pregnancies.

Prediction of newborn birth weight based on the estimation at 20-24 weeks of gestation

OBJECTIVE

The aim of this study was to develop a mathematical equation to predict the birth weight during the second trimester at 20-24 weeks of gestation.

MATERIALS AND METHODS

In a university hospital, 110 healthy pregnant women were eligible for inclusion at 20-24 weeks of gestation. We recorded the maternal weight (pre-pregnancy, mid-pregnancy, and at delivery) and body mass index (BMI), newborn birth weight, time period from ultrasound examination to term delivery, and also the fetal biometrics sonographically at 20-24 weeks of gestation. Pearson's correlation was used to verify the extent of the relationship between all the above measurements and the newborn birth weight. Multiple regressions with the stepwise method were used to analyze maternal weight factors, fetal biometrical factors, and pregnancy interval. An equation for term birth weight estimation during the second trimester was determined.

RESULTS

Maternal BMI at mid-pregnancy, time interval from mid-pregnancy to term, and abdominal circumference had the highest correlation with newborn birth weight (r = 0.388, 0.341, and 0.315, respectively, p < 0.05). Using the stepwise regression analysis, an optimal formula with variance of 0.303 was derived: estimated birth weight = -700 + 49.766 × (mid-pregnancy BMI [kg/m2]) + 13.362 × (time interval from mid-pregnancy to term delivery [days]) + 68.696 × (abdominal circumference [cm]).

CONCLUSION

We propose an accurate, simple, and easy formula to better assess the newborn birth weight at mid-pregnancy for the Asian population. Mid-pregnancy BMI was a more significant factor for birth weight estimation than other maternal weight factors in this study.

Estimation of fetal weight in fetuses with abdominal wall defects: comparison of 2 recent sonographic formulas to the Hadlock formula

OBJECTIVE

Estimation of fetal weight is particularly challenging in fetuses with abdominal wall defects (AWDs). We sought to compare the accuracy and screening efficiency for intrauterine growth restriction (IUGR) of 2 recent sonographic formulas to those of the Hadlock formula (Am J Obstet Gynecol 1985; 151:333-337) in fetuses with AWDs.

METHODS

This was a retrospective cohort study of fetuses with AWDs. Fetuses with sonographically estimated fetal weights (EFWs) within 14 days before delivery were included. Using the individual biometric measurements, EFWs were calculated using the Honarvar (Int J Gynaecol Obstet 2001; 73:15-20; femur length [FL]), Siemer (Ultrasound Obstet Gynecol 2008; 31:397-400; FL, biparietal diameter [BPD], and occipitofrontal diameter), and Hadlock (BPD, head circumference, abdominal circumference, and FL) formulas. The calculated EFWs were adjusted for interval growth between the dates of sonography and delivery using published sonographic fetal growth velocity standards. Accuracy and screening efficiency for IUGR were compared.

RESULTS

Seventy-six fetuses were included: 53 with gastroschisis and 23 with omphalocele. The median gestational age at delivery was 36.6 weeks (range, 25.0 to 39.0 weeks). The Siemer formula had the lowest mean percentage error (-2.5% [95% confidence interval (CI), -6.2% to +1.2%]) without systematic bias (P = .182). The Hadlock formula had the highest precision (random error, 11.4%), sensitivity (91%), and accuracy for predicting IUGR (85% [95% CI, 77% to 94%]).

CONCLUSIONS

None of the 3 sonographic formulas is ideal for estimating fetal weight in fetuses with AWDs. The Siemer formula should be used when accuracy in the absolute EFW is the goal. For the purpose of making the more clinically relevant diagnosis of IUGR, use of the Hadlock formula is justified.

Estimation of birth weight by two-dimensional ultrasonography: a critical appraisal of its accuracy

OBJECTIVE

To assess the accuracy and characterize two-dimensional ultrasonographic formulas for the estimation of birth weight according to the type of fetal biometric parameters these formulas rely on to make fetal weight predictions.

METHODS

A prospective recruitment of 589 pregnant women was carried out for this cross-sectional study. Different biometric parameters were taken ultrasonographically to estimate birth weight using 35 different formulas. Only those patients who delivered within 48 hours were considered for the analysis (n=441). Differences between the estimated and actual birth weight were assessed by percentage error, accuracy in predictions within +/-10% and +/-15% of error, and use of the Bland-Altman method. All formulas were assessed individually and clustered on the basis of the type of fetal biometric information that they incorporate.

RESULTS

Twenty-nine formulas provided an overall mean absolute percentage error less than or equal to 10%, with overall predictions within +/-10% and +/-15% of the actual birth weight (69.2% and 86.5%, respectively). Twenty formulas showed a good accuracy (bias 0.50 or less) and low variability (mean standard deviation 1.2). Among the categorized algorithms, formulas based on head-abdomen-femur measurements showed the lowest mean absolute percentage error. Upon stratification for birth weight, the group of formulas that rely on abdomen and femur measurements performed best for fetuses weighing more than 3,500 g (P<.01).

CONCLUSION

Our findings show that most formulas are relatively accurate at predicting birth weight up to 3,500 g, and all algorithms tend to underestimate large fetuses.

LEVEL OF EVIDENCE

III.

Sonographic fetal weight estimation using femoral length: Honarvar equation

BACKGROUND

Fetal growth is the result of interactions between various factors and can be estimated by ultrasonic measurements. Fetal femur length is a scale for estimating the fetal weight in individual races because fetal growth patterns differ among different races.

SUBJECTS AND METHODS

This was a prospective study involving 500 pregnant women at 36 weeks of gestational age. Real-time sonography was done to measure the femoral length and then the weight of the fetus was estimated by the Honarvar 2 equation. The correlation between estimated fetal weight (EFW) and real weight was tested by Pearson correlation coefficient and relationships with the age and BMI of the mother, the sex of the neonate and parity were tested by multiple regression.

RESULTS

EFW by the Honarvar 2 equation correlated significantly with the actual birthweight. Therefore, this equation is valid for fetal weight estimation. It also does not depend on the age and BMI of the mother, sex of neonate, or parity.

CONCLUSION

Ethnicity potentially plays an important role in the fetal weight estimation. The Honarvar formula produced the best estimate of the actual birthweight for Iranian fetuses, and its use is recommended.

Can the growth factors PTHrP, Ihh and VEGF, together regulate the development of a long bone?

Endochondral ossification is the process of differentiation of cartilaginous into osseous tissue. Parathyroid hormone related protein (PTHrP), Indian hedgehog (Ihh) and vascular endothelial growth factor (VEGF), which are synthesized in different zones of the growth plate, were found to have crucial roles in regulating endochondral ossification. The aim of this study was to evaluate whether the three growth factors PTHrP, Ihh and VEGF, together, could regulate longitudinal growth in a normal human, fetal femur. For this purpose, a one-dimensional finite element (FE) model, incorporating growth factor signaling, was developed of the human, distal, femoral growth plate. It included growth factor synthesis in the relevant zones, their transport and degradation and their effects. Simulations ran from initial hypertrophy in the center of the bone until secondary ossification starts at approximately 3.5 months postnatal. For clarity, we emphasize that no mechanical stresses were considered. The FE model showed a stable growth plate in which the bone growth rate was constant and the number of cells per zone oscillated around an equilibrium. Simulations incorporating increased and decreased PTHrP and Ihh synthesis rates resulted, respectively, in more and less cells per zone and in increased and decreased bone growth rates. The FE model correctly reflected the development of a growth plate and the rate of bone growth in the femur. Simulations incorporating increased and decreased PTHrP and Ihh synthesis rates reflected growth plate pathologies and growth plates in PTHrP-/- and Ihh-/- mice. The three growth factors, PTHrP, Ihh and VEGF, could potentially together regulate tissue differentiation.