A New Sonographic Weight Estimation Formula for Fetuses with Congenital Diaphragmatic Hernia

PURPOSE

The accuracy of the sonographic weight estimation (WE) of fetuses with congenital diaphragmatic hernia (CDH) is significantly lower than that of fetuses without any malformations. The objective of this study was to develop and evaluate the first specific sonographic weight formula for fetuses with CDH.

MATERIALS AND METHODS

In a retrospective, multicenter, cohort study, a statistical estimation technique known as "multivariable fractional polynomial regression" was applied to a group of 146 fetuses with CDH. Each fetus underwent an ultrasound examination with complete biometric parameters within 7 days of delivery. A new formula was derived using the obtained data and was then compared with other commonly used equations. The accuracy of the different formulas was compared using means of signed percentage errors (SPE), medians of absolute percentage errors (MAPE), and fractions of estimates within prespecified error bounds.

RESULTS

The new derived formula is: EFW = 10^(4.6729 107 371 + 0.2365 011 768 * HC + 0.2228 897 682 * FL^2 - 0.0129 895 773 * FL^3 - 1.0470 039 072 * (FL * HC)^0.5 + 0.0004 314 661 * (AC * HC) - [in case of liver herniation] 0.0062 112 122), where EFW is the estimated fetal weight, HC is the head circumference, AC is the abdominal circumference, and FL is the femur length. The new formula proved to be superior to other established equations, showing both the lowest median absolute percentage error (MAE: 6.97) and mean signed percentage error (SPE: 0.40), and the best distribution of absolute percentage errors within prespecified error bounds.

CONCLUSION

This new formula significantly improves weight estimation in fetuses with CDH.

Sonographic weight estimation in fetuses with congenital diaphragmatic hernia

PURPOSE

To determine the accuracy of sonographic weight estimation (WE) for fetuses with congenital diaphragmatic hernia (CDH), and to assess whether certain sonographic models perform better than others in cases of CDH.

MATERIAL AND METHODS

In a retrospective, multicenter cohort study, the accuracy of WE in fetuses with CDH (n = 172) was evaluated using eight sonographic models and was compared with a control group of fetuses without malformations (n = 172). Each fetus underwent ultrasound examination with complete biometric parameters within 7 days of delivery. The accuracy of the different formulas was compared using means of percentage errors (MPE), medians of absolute percentage errors (MAPE), and proportions of estimates within 10 % of actual birth weight.

RESULTS

Fetuses with CDH had a significantly lower abdominal circumference (AC) in comparison with the control group (293.6 vs. 312.0 mm, p < 0.001). All of the formulas tested in fetuses with CDH, except for the Siemer equation (the only model that does not incorporate any abdominal measurements), showed significantly lower (more negative) MPEs, larger MAPEs, and smaller proportions of estimates within 10 % of actual birth weight in comparison with the control group. 

CONCLUSION

The accuracy of sonographic WE in fetuses with CDH is significantly poorer than in fetuses without malformations, principally because of a larger systematic error due to artificially small AC measurements. The development of new, specific models derived from fetuses with CDH could improve the accuracy of WE for infants with this condition.

[Expectations of pregnant women on an ideal maternity hospital]

PURPOSE

The aim of this study was to evaluate expectations of pregnant women on an ideal maternity hospital.

MATERIAL AND METHODS

We prospectively performed a survey among 566 pregnant women with regard to their expectations on a perfect hospital for obstetrics. Data collection was accomplished in 3 obstetrical departments in Mannheim, Germany. The questionnaire contained 23 general questions about sociodemographic characteristics and 34 specific questions about the anticipated childbirth. Women who were less than 20 weeks pregnant and women who did not speak German fluently were excluded from this study.

RESULTS

In our survey the possibility to get to know midwifes and doctors at information evenings and a guided delivery room tour were defined as very important factors by the interviewed women. Of particular importance was a continuous care by a single midwife and the physical attendance of a family member during childbirth. Furthermore, friendliness of the staff and medical care by paediatricians after childbirth were identified to be important. To some extent, a modern appearance of the ward was also a matter of importance.

CONCLUSIONS

The medical treatment of mother and the newborn child and the friendliness of the staff have been identified as the most important factors with regard to the expectations of women on an ideal maternity hospital. In addition, a pleasant ambiance of the ward and regular visits by a lactation specialist were named as important.

Fetal weight estimation in extreme macrosomia (≥ 4,500 g): comparison of 10 formulas

PURPOSE

The aim of this retrospective study was to compare the accuracy of 10 commonly used weight estimation formulas in a group of fetuses with extreme macrosomia ( ≥ 4 ,500 g).

MATERIALS AND METHODS

Ten formulas were evaluated in a group of 174 fetuses with a birth weight (BW) ≥ 4 ,500 g. Each fetus underwent ultrasound examination with complete biometric parameters within 7 days of delivery. The accuracy of the different formulas for fetal weight estimation (EFW) was compared by mean percentage error (MPE), median of the absolute percentage error (MAPE), the "limits-of-agreement" method and the percentage of EFW falling within the 10 % range of the true birth weight.

RESULTS

MPE showed the largest deviation from zero with the Schild formula (MPE - 15.43 %) and the Shepard formula (MPE + 6.08 %) and was closest to zero with the Hadlock II formula (MPE - 5.34 %). The MPE of all formulas showed significant bias when compared to zero. All tested formulas, except the Shepard and Shinozuka equations, significantly underestimated fetal weight. The lowest MAPE was found for the Merz formula (7.23 %). The Hadlock II formula obtained the highest percentage of EWF within the 10 % range of the true birth weight (66.1 %).

CONCLUSION

Exact weight estimation in extreme macrosomia remains an unsolved problem, and can therefore only conditionally provide a sufficient basis for clinical decision processes.

A new formula for optimized weight estimation in extreme fetal macrosomia (≥ 4500 g)

PURPOSE

To develop and to evaluate a specific sonographic weight formula for fetuses with extreme macrosomia (≥ 4500 g).

MATERIALS AND METHODS

A statistical estimation technique known as "gradient boosting with component-wise P-splines" was applied to a group of 174 fetuses with a birth weight (BW) ≥ 4500 g. Each fetus underwent an ultrasound examination with complete biometric parameters within 7 days of delivery. The exclusion criteria were multiple pregnancy, intrauterine death, and major structural or chromosomal anomalies. A new formula was derived using the obtained data and was then compared to currently available equations for estimating weight in the macrosomic fetus.

RESULTS

The new formula is: log10 (EFW) = 3.6687781710 - 0.0003230278 × (BPD - 100.4080) - 0.0000843433 × (BPD - 100.4080)^2 + 0.0007281281 × (OFD - 120.6322) + 0.0000664323 × (OFD - 120.6322)^2 + 0.000000001794019 × exp(ATD - 120.1552) + 0.0005946974 × (APAD - 121.2069) - 0.0000210137 × (APAD - 121.2069)^2 - 0.000003318 × (APAD - 121.2069)^3, where EFW is the estimated fetal weight, BPD is the biparietal diameter, OFD is the occipitofrontal diameter, ATD is the abdominal transverse diameter, and APAD is the abdominal anteroposterior diameter. The new formula proved to be superior to other established equations, showing the lowest mean absolute percentage error (MAE 2.506), the smallest variance regarding the signed percentage error (SPE) (SD 3.376), and the best distribution of absolute percentage errors within prespecified error bounds.

CONCLUSION

This new formula significantly improves weight estimation in fetuses with extreme macrosomia.

New sonographic method for fetuses with small abdominal circumference improves fetal weight estimation

PURPOSE

Accurate estimation of fetal weight is a valuable tool for determining further obstetric management. Commonly used weight formulas lack accuracy, even though some equations appear to be favorable within defined weight ranges. However, due to the fact that fetal weight is not known in advance, it is not always clear which formula is suitable. In most of the commonly used equations, the fetal abdominal circumference (AC) is not only included but also has the greatest impact on weight estimation. The aim of our study was to develop and evaluate a new formula specifically designed for a small fetal AC in order to improve weight estimation.

MATERIALS AND METHODS

The study included 323 pregnancies. The inclusion criteria were singleton pregnancy, ultrasound examination with complete biometric parameters and an AC ≤ 29.0 cm within 7 days of delivery, and an absence of structural or chromosomal malformations. Two "best-fit" formulas were derived by forward regression analysis. Finally, the accuracy of the new formulas was compared to commonly used weight equations by using the percentage error, absolute percentage error (APE), limits of agreement (LOA) and cumulative distribution.

RESULTS

Contrary to the routine methods, which significantly underestimated fetal weight, the new formulas did not have a systematic error. The medians of the APE were the lowest (7.13 and 7.16) when compared to other equations. Moreover, the new formulas demonstrated the narrowest LOA. At all discrepancy levels (5%, 10%, 15%, and 20%), the new formulas included significantly more cases than the commonly used methods.

CONCLUSION

The specifically designed equations help to improve fetal weight estimation for fetuses with an AC ≤ 29.0 cm. For optimal weight estimation, we recommend using the new formula II.

New sonographic method for fetuses with a large abdominal circumference improves fetal weight estimation

PURPOSE

Birth weight (BW) is an important prognostic parameter for neonatal morbidity and mortality. Commonly used weight formulas lack accuracy, especially at the lower and upper end of the fetal weight range. Fetal abdominal circumference (AC) as part of most of the commonly used equations has the greatest impact on weight estimation. It has been shown that formulas specifically designed for a small fetal AC can improve weight estimation. The aim was to find out whether a new formula specifically designed for fetuses with a large AC may also improve weight determination.

MATERIALS AND METHODS

The study included 830 singleton pregnancies. The inclusion criteria were ultrasound examination with complete biometric parameters and an AC ≥ 36.0 cm within 7 days of delivery, and an absence of structural or chromosomal malformations. Two "best-fit" formulas were derived by forward regression analysis. The accuracy of the new formulas was compared with commonly used weight equations using percentage error (PE), absolute percentage error (APE), limits of agreement (LOA) and cumulative distribution.

RESULTS

New formula I had no systematic error while new formula II and the routine methods significantly overestimated fetal weight. The medians of the APE were the lowest among the new equations (5.77 and 7.25). The new formulas also demonstrated the narrowest LOA. Importantly, at all discrepancy levels (5 %, 10 %, 15 %, and 20 %), new formula I included significantly more cases than the commonly used methods.

CONCLUSION

These specifically designed equations help to improve fetal weight estimation for fetuses with an AC ≥ 36.0 cm. For optimal weight estimation, we recommend using new formula I.

What are the limits of accuracy in fetal weight estimation with conventional biometry in two-dimensional ultrasound? A novel postpartum study

OBJECTIVE

Commonly used formulae for fetal weight estimation, including combinations of several biometric parameters, lack accuracy despite efforts to improve them. This study aimed to investigate the limits of fetal weight estimation based on conventional biometric parameters on two-dimensional (2D) ultrasound by developing and evaluating new weight equations using postpartum biometric parameters.

METHODS

This was a prospective multicenter study including 628 singleton pregnancies at term. Inclusion criteria were healthy newborns with no physical or chromosomal malformations. Postpartum measurement of head circumference, abdominal circumference and thigh length was performed. Six 'best-fit' formulae were derived using forward regression analysis in a formula-finding group (n = 419), and their accuracy was compared with birth weight in an evaluation group (n = 209) using percentage error, absolute percentage error, limits of agreement and the proportion of weight estimations falling within a discrepancy level of ± 10%.

RESULTS

The new formulae showed no systematic error, with SD for the percentage error between 7.42 and 8.77 and no significant differences between median absolute percentage errors (4.84-5.71). They included 74.6-81.3% of neonates within a discrepancy level of 10%. With regard to the 95% limits of agreement, weight estimates were within a range of about ± 500 g.

CONCLUSION

These results show that a good sonographic weight formula has the following features: no systematic error, an SD of about 7% and inclusion of 80% of cases within a discrepancy level of 10%. The study indicates that the current accuracy of fetal weight estimation with conventional biometric parameters by 2D ultrasound has reached its limits. Further improvement will probably only be achieved through new approaches in ultrasonography.

Prediction of chronic lung disease, survival and need for ECMO therapy in infants with congenital diaphragmatic hernia: additional value of fetal MRI measurements?

INTRODUCTION

The lung-to-head ratio (LHR), measured by ultrasound, and the fetal lung volume (FLV), measured by MRI, are both used to predict survival and need for extra corporeal membrane oxygenation (ECMO) in infants with congenital diaphragmatic hernia (CDH). The aim of this study is to determine whether MRI measurements of the FLV, in addition to standard ultrasound measurements of the LHR, give better prediction of chronic lung disease, mortality by day 28 and need for ECMO.

MATERIALS AND METHODS

Patients with unilateral isolated CDH born between January 2002 and December 2008 were eligible for inclusion. LHR and FLV were expressed as observed-to-expected values (O/E LHR and O/E FLV). Univariate and multivariate analyses were performed. Receiver operating characteristic curves were constructed and areas under the curve (AUC) were calculated to determine predictive values.

RESULTS

90 patients were included in the analysis. Combined measurement of the O/E LHR and O/E FLV gave a slightly better prediction of chronic lung disease (AUC=0.83 and AUC=0.87) and need for ECMO therapy (AUC=0.77 and AUC=0.81) than standard ultrasound measurements of the O/E LHR alone. Combined measurement of the O/E LHR and O/E FLV did not improve prediction of early mortality (AUC=0.90) compared to measurement of the O/E LHR alone (AUC=0.89). An intrathoracal position of the liver was independently associated with a higher risk of early mortality (p<0.001), chronic lung disease (p=0.007) and need for ECMO therapy (p=0.001).

DISCUSSION

Chronic lung disease and need for ECMO therapy are slightly better predicted by combined measurement of the O/E LHR and the O/E FLV. Early mortality is very well predicted by measurement of the O/E LHR alone.

CONCLUSION

Clinical relevance of additional MRI measurements may be debated.

[Massive increase of foetal abdominal circumference due to hereditary polycystic kidney disease]

Autosomal recessive polycystic kidney disease (ARPKD) is a rare condition with a poor prognosis. We report on a 30-year-old primagravid woman in the 34th) week of gestation who was admitted to our hospital. ARPKD of the foetus had been sonographically suspected since the 26th week of gestation. Ultrasound examination showed big polycystic kidneys on both sides. The non-consanguineous parents wanted a maximum therapy for the infant. Foetal digitalisation because of heart insufficiency and prophylactic lung maturation was started. In the further course, Doppler sonographic values worsened and a Caesarean section was performed in the 34th week of gestation at the demand of the parents and due to the expected problems in case of a vaginal delivery. The weight of the newborn was 3,780 g and the abdominal circumference was 50 cm. The newborn was intubated immediately after birth and artificial ventilation was performed. Extracorporeal membrane oxygenation was not possible due to the bad cardial condition. The boy died 16 h after delivery. The parents refused genetic examination and autopsy of the newborn. ARPKD is a severe disease that may have obstetric relevance, due to the massively increased abdominal circumference. Therefore, termination of pregnancy or preterm induction of labor should be considered in order to avoid Caesarean section. Additionally, early prenatal diagnosis with genetic analysis of PRKD1 in cases of suspected ARPKD can be helpful.

Do specific weight formulas for fetuses < or = 1500 g really improve weight estimation?

PURPOSE

In addition to gestational age, fetal weight is an important predictive parameter for neonatal morbidity and mortality in very small fetuses. In order to improve weight estimation, specific weight formulas for fetuses under 1500 g have been introduced by several authors. The aim of the present study was therefore to compare specific weight equations for fetuses under 1500 g with widely used methods that were designed for the whole fetal weight range.

MATERIALS AND METHODS

459 pregnancies were included in order to evaluate six widely used formulas and four formulas specifically designed for very small fetuses. The inclusion criteria were a singleton pregnancy, birth weight equal to or less than 1500 g, ultrasound examination with complete biometric parameters during the 7 days prior to delivery, and an absence of structural or chromosomal malformations.

RESULTS

All formulas, except the Hadlock equations, demonstrated a significant systematic error. Regarding the random error, it was similar for most of the methods. The Scott formula showed the narrowest limits of agreement. At a discrepancy level of 5 % and 10 % between estimated fetal weight and actual birth weight, one of the Hadlock formulas included the most cases.

CONCLUSION

Weight formulas, specifically designed for very small fetuses, do not improve sonographic weight estimation substantially. Among these formulas, the Scott equation was the most accurate one. However compared to the widely used Hadlock formulas, it was not favorable.

Macrosomia: a new formula for optimized fetal weight estimation

OBJECTIVES

To develop and test a specific formula for estimating weight in the macrosomic fetus.

METHODS

Ultrasound estimations of fetal weight were carried out within 1 week of delivery in 424 singleton fetuses with a birth weight of > or = 4000 g. Exclusion criteria were multiple pregnancy, intrauterine death and major structural or chromosomal anomalies. Stepwise regression modeling was used to derive a prediction formula with birth weight as the dependent variable and maternal booking weight and fetal biometric measurements as independent parameters. After a new formula for estimated fetal weight (EFW) had been developed in a formula-finding group (n = 284), it was compared with commonly used weight equations (evaluation group, n = 140).

RESULTS

The new formula (log(e)EFW = 7.6377445039 + 0.0002951035 x maternal weight + 0.0003949464 x head circumference + 0.0005241529 x abdominal circumference + 0.0048698624 x femur length) proved to be superior to established equations, with the smallest mean error (mean +/- SD, -10 +/- 202 g), the smallest mean percentage error (mean +/- SD, -0.03 +/- 4.6%) and the lowest mean absolute percentage error (3.69 (range, 0.05-13.57)%) when studied in the evaluation group. With the new formula, 77.9% of estimates fell within +/- 5% of the actual weight at birth, 97.1% within +/- 10%, and 100% within +/- 15% and +/- 20%.

CONCLUSIONS

The new formula allows better weight estimation in the macrosomic fetus.

A new sonographic weight formula for fetuses <or= 2500 g

PURPOSE

Birth weight is an important predictive parameter for neonatal morbidity and mortality in the small fetus. Accurate estimation of fetal weight is therefore a valuable tool for determining the further obstetric management. The majority of studies presenting new formulas have included relatively small samples with a narrow range of birth weights, mostly term fetuses. In a previous study, we evaluated several weight formulas over the whole range of birth weights and in defined subgroups. We were able to show that some regression formulas appeared to be favorable within these subgroups. Notably, the highest levels of inaccuracy were found in the group of infants with a birth weight of less than 2500 g. This led us to hypothesize that a formula based on the lower birth weight group might increase the accuracy of weight estimation. The aim of the present study was therefore to develop a new specific formula for estimating weight in fetuses less than or equal to 2500 g and to compare the new regression formula with commonly used weight equations.

MATERIALS AND METHODS

This study included 260 pregnancies. The inclusion criteria were a singleton pregnancy; birth weight equal to or less than 2500 g; an ultrasound examination with complete biometric parameters within 7 days prior to delivery; and an absence of structural or chromosomal malformations. The data for the first 130 newborns were used to develop a new formula. The remaining 130 infants were used to evaluate the new regression formula and to compare it to commonly used weight equations. Stepwise regression analysis was carried out with the birth weight as the dependent variable and biometric parameters as independent parameters to obtain the best-fit formula.

RESULTS

The mean absolute percentage error for the new formula was 7.71 %. Compared to the other formulas, it generated the highest intraclass correlation coefficient. By the limits of agreement, the new formula demonstrated only a slight tendency towards underestimating fetal weight, and it provided the smallest range of all weight equations.

CONCLUSION

With proper application, our new formula can improve the accuracy of fetal weight estimation.

Three-dimensional power Doppler sonography of the (sub)endometrium and angiogenic cytokine concentrations

The aim of this study was to determine the correlation between three-dimensional power Doppler sonography (3D-PDS) of the (sub)endometrium and concentrations of angiogenic cytokines in patients attending an IVF programme. A total of 42 patients was included in a prospective, non-randomized clinical study. 3D-PDS of the (sub)endometrium was performed on the day of oocyte aspiration, with and without contrast agent. Quantitative assessment included the following 3D Doppler parameters: vascularization index, flow intensity, and vascularization flow index. On the same day, concentrations of oestradiol (serum only), vascular endothelial growth factor (VEGF), insulin-like growth factor (IGF) 1, IGF-binding protein 3 (IGFBP-3) and leptin were determined in the serum and in the follicular fluid. All 3D-PDS indices were significantly higher with contrast enhancement (P < 0.05). Follicular fluid concentrations of VEGF and IGFBP-3, as well as serum concentrations of leptin, showed significant P-values when correlated with (sub)endometrial Doppler indices. A weak linear dependency appeared between flow intensity and VEGF and leptin. Furthermore, weak dependencies were apparent between 3D Doppler parameters and high follicular fluid concentrations of VEGF and IGFBP-3. It is concluded that there is only little evidence for an association between (sub)endometrial Doppler indices as assessed by 3D-PDS and concentrations of angiogenic cytokines.

Weight estimation by three-dimensional ultrasound imaging in the small fetus

OBJECTIVES

To improve birth weight estimation in fetuses weighing <or= 1600 g at birth by deriving a new formula including measurements obtained using three-dimensional (3D) sonography.

METHODS

In a prospective cohort study, biometric data of 150 singleton fetuses weighing <or= 1600 g at birth were obtained by sonographic examination within 1 week before delivery. Exclusion criteria were multiple pregnancy, intrauterine death as well as major structural or chromosomal anomalies. A new formula was derived using our data, and was then compared with currently available equations for estimating weight in the preterm fetus.

RESULTS

Different statistical estimation strategies were pursued. Gradient boosting with component- wise smoothing splines achieved the best results. The resulting new formula (estimated fetal weight = 656.41 + 1.8321 x volABDO + 31.1981 x HC + 5.7787 x volFEM + 73.5214 x FL + 8.3009 x AC - 449.8863 x BPD + 32.5340 x BPD(2), where volABDO is abdominal volume determined by 3D volumetry, HC is head circumference, volFEM is thigh volume determined by 3D volumetry, FL is femur length and BPD is biparietal diameter) proved to be superior to established equations in terms of mean squared prediction errors, signed percentage errors and absolute percentage errors.

CONCLUSIONS

Our new formula is relatively easy to use and needs no adjustment to weight percentiles or to fetal lie. In fetuses weighing <or= 1600 g at birth it is superior to weight estimation by traditional formulae using two-dimensional measurements.

How good is fetal weight estimation using volumetric methods?

PURPOSE

Birth weight is an important predictive parameter for neonatal morbidity and mortality, and accurate estimation of fetal weight is therefore a valuable tool for determining the further obstetric management. Many sonographic weight formulas have been introduced. Most of these widely accepted formulas were derived from non-linear regression analysis. Only few formulas have been constructed using other methods, such as the physically based volumetric method based on routine two-dimensional biometric parameters in the fetus. The rationale for calculating fetal weight from volumetric measurements was that weight should to be directly proportional to fetal volume. In a recent review by Dudley, this method was considered to have some advantages in comparison with conventional regression formulas. However, to the best of our knowledge, none of the published volumetric formulas has ever been evaluated in a large population of fetuses. The aim of this study was to compare the volumetry-based formulas with widely accepted weight equations derived from regression analysis. We evaluated weight equations over the whole weight range and in specific weight groups in order to find out whether some equations were preferable in the groups tested.

MATERIALS AND METHODS

3975 pregnancies were included in order to evaluate four conventional formulas and four formulas based on volumetric models. The inclusion criteria were a singleton pregnancy, ultrasound examination with complete biometric parameters within 7 days before delivery, and an absence of structural or chromosomal malformations. The equations were compared over the whole weight range and in specific weight groups.

RESULTS

Over the whole weight range, no single formula was able to offer a substantial advantage. In the small fetus, the Hadlock formula was preferable due to its low level of systematic error. For mid-sized fetuses, the Schild formula should be considered. In macrosomic fetuses, all formulas tended to underestimate the actual birth weight. Here, the best accuracy was achieved using the Merz formula.

CONCLUSION

Neither a volumetric formula nor a conventional formula proved to be superior over the whole weight range. Within specific weight groups, some formulas showed improved accuracy. However, new approaches such as three-dimensional ultrasonography need to be pursued further in order to achieve better results in fetal weight estimation.

Fetal weight estimation by ultrasound: comparison of 11 different formulae and examiners with differing skill levels

PURPOSE

Fetal weight is an important predictive parameter of neonatal morbidity and mortality. Precise estimation of fetal weight is therefore a valuable item of information for further prenatal and obstetric management. Many regression formulae for sonographic fetal weight estimation have been published during the last 30 years, which, unfortunately, generally show poor rates of accuracy. The aim of this study was to compare commonly used formulae in different birth weight groups in order to assess whether any of the formulae are more or less favourable. The second purpose was to estimate the role of examiners on the accuracy of fetal weight estimation.

MATERIALS AND METHODS

11 different formulae were evaluated in a group of 1941 pregnancies. Each fetus underwent ultrasound examination with complete biometric parameters within seven days before delivery. The assessment was carried out by either experienced or inexperienced sonographers.

RESULTS

Over the whole weight range and in the subgroup of newborns with a birth weight less than 2500 g (n = 160), two Hadlock regression formulae (including abdominal circumference, femur length, head circumference, biparietal diameter, and abdominal circumference, femur length, biparietal diameter, respectively) showed the best levels of accuracy. Infants with a birth weight between 2500 and 3999 g (n = 1570) were best estimated using the gender-specific Schild formula. Macrosomic newborns (n = 211) were best evaluated using Merz's regression formula. The more skilled sonographers were able to achieve much higher intraclass correlation coefficients for all formulae.

CONCLUSION

Some regression formulae appear to be favourable within defined weight ranges. Accuracy of the formulae, however, is still unsatisfactory, and new formulae focusing on specific weight ranges (e. g., macrosomic fetuses) are needed. In addition, experience in obstetric ultrasound improves accuracy of fetal weight estimation.

Specific weight formula for fetuses with abdominal wall defects

OBJECTIVES

To develop and to evaluate a specific sonographic weight formula for fetuses with abdominal wall defects.

METHODS

For formula finding, 380 preterm singleton pregnancies without fetal anomalies were included. Ultrasound examinations with complete biometric parameters were performed within 7 days before delivery. Stepwise regression analysis was carried out with birth weight as the dependent variable and sonographic parameters (abdominal measurements not included) as independent variables to obtain the best-fit formula. The new equation was evaluated in a group of 97 fetuses with either gastroschisis or omphalocele.

RESULTS

In the evaluation group, the mean (SD) percentage error of the new equation was -0.84 (12.03), showing no systematic bias. The mean absolute percentage error was 9.29. The new specific method provided significantly greater accuracy than commonly used formulae.

CONCLUSIONS

This specific weight formula for fetuses with abdominal wall defects is an accurate method of estimating fetal weight.

[Eye disease and mode of delivery]

Many ophthalmologists and obstetricians recommend either an assisted vaginal delivery with forceps or vacuum extraction or a Caesarean section in cases of pre-existing eye diseases such as severe myopia, retinal detachment, diabetic retinopathy, or glaucoma. These recommendations, however, are not evidence-based. None of the published trials have reported any retinal changes after vaginal delivery. In general, eye disease is not an indication for an instrumental or operative delivery provided that regular eye examinations (once each trimester) have been performed.