Comparison of clinical versus ultrasound estimation of fetal weight

Fetal weight estimation in tall women: is ultrasound more accurate than clinical assessment? A prospective trial

PURPOSE

Estimated fetal weight (EFW) is crucial for clinical decision-making during pregnancy and labor. Maternal habitus impacts its accuracy. This study compared the accuracy of clinical versus ultrasound EFW in tall pregnant women (height ≥ 172 cm, 90th percentile).

METHODS

In this prospective study, tall pregnant women at term, who arrived for a prenatal visit and delivered within a week, underwent clinical and ultrasound assessments of estimated fetal weight. Each woman served as her own control. After delivery, birth weight was compared to the clinical and ultrasound EFW. The primary outcome was the accuracy of each method in predicting the actual birth weight.

RESULTS

All 100 women included in this trial underwent clinical and ultrasound estimations of fetal weight. Mean maternal height was 175.7 ± 3.3 (172-185) cm. More clinical EFW swere inaccurate compared to ultrasound (25 (25%) vs. 6 (6%), respectively, p < 0.001). Both clinical (3583 g) and ultrasound (3490 g) evaluations underestimated the fetal weights compared to the birth weights (3664 g, p < 0.001). In the macrosomic fetal group, both the clinical (3983 g) and ultrasound (3767 g) estimates were significantly inaccurate compared to the birth weights (4237 g, p < 0.001).

CONCLUSION

Among tall women, ultrasound EFW is more accurate than clinical EFW.

TRIAL REGISTRATION NUMBER AND DATE OF REGISTRATION

IRB-0016-17-MMC, Clinical-Trials.gov identifier NCT03206281.

Estimation of fetal weight: a comparison of clinical and sonographic methods

Fetal weight estimation is important in the management of labour and delivery. This study aimed to compare the accuracy of the clinical and ultrasound methods of fetal weight estimation. This was a prospective study involving 110 term cephalic singleton pregnancies delivered within 24 hours of clinical fetal weight estimation using Johnson's and Dare's formulae and ultrasound estimation at a Tertiary hospital in Abakaliki, Nigeria. The data were analysed with Stata 11 software. The sonographic estimation within 10% of the actual birth weight (ABW) of 68.2% was significantly greater than the accuracy of Johnson's (23.6%), Dare's (26.4%), and the combined clinical formulae (27.1%). The clinical methods overestimated the fetal weight. Both methods showed a positive correlation with the ABW. In conclusion, the sonographic method had a better accuracy than the clinical methods. However, fetal weight overestimation by clinical methods warrants their usefulness in resource-poor settings such that the clinical determination of a normal weight foetus will exclude fear of complications from macrosomia. Impact statement What is already known on this subject? An accurate estimation of fetal weight is important in the management of labour and delivery. However, there is limited evidence that any of the available methods of fetal weight estimation is more accurate than the others. What do the results of this study add? This study showed that the clinical methods using Johnson's and Dare's formulae had a significantly higher mean percentage and absolute mean percentage error compared to the sonographic estimation of fetal weight. The sonographic estimation within 10% of actual birth weight (ABW) of 68.2% was significantly greater than that of Johnson's and Dare's formulae with 23.6% and 26.4%, respectively. All of the methods showed a positive correlation with the ABW. What are the implications of these findings for clinical practice and/or further research? This implies that the sonographic method has a better accuracy than the clinical methods in estimating the fetal weight. However, the overestimation of fetal weight by the clinical methods warrants their usefulness in resource-poor settings such that the clinical determination of a normal weight foetus will exclude the fear of complications from macrosomia.

Fetal weight estimation at term - ultrasound versus clinical examination with Leopold's manoeuvres: a prospective blinded observational study

BACKGROUND

Fetal weight estimation is of key importance in the decision-making process for obstetric planning and management. The literature is inconsistent on the accuracy of measurements with either ultrasound or clinical examination, known as Leopold's manoeuvres, shortly before term. Maternal BMI is a confounding factor because it is associated with both the fetal weight and the accuracy of fetal weight estimation. The aim of our study was to compare the accuracy of fetal weight estimation performed with ultrasound and with clinical examination with respect to BMI.

METHODS

In this prospective blinded observational study we investigated the accuracy of clinical examination as compared to ultrasound measurement in fetal weight estimation, taking the actual birth weight as the gold standard. In a cohort of all consecutive patients who presented in our department from January 2016 to May 2017 to register for delivery at ≥37 weeks, examination was done by ultrasound and Leopold's manoeuvres to estimate fetal weight. All examiners (midwives and physicians) had about the same level of professional experience. The primary aim was to compare overall absolute error, overall absolute percent error, absolute percent error > 10% and absolute percent error > 20% for weight estimation by ultrasound and by means of Leopold's manoeuvres versus the actual birth weight as the given gold standard, namely separately for normal weight and for overweight pregnant women.

RESULTS

Five hundred forty-three patients were included in the data analysis. The accuracy of fetal weight estimation was significantly better with ultrasound than with Leopold's manoeuvres in all absolute error calculations made in overweight pregnant women. For all error calculations performed in normal weight pregnant women, no statistically significant difference was seen in the accuracy of fetal weight estimation between ultrasound and Leopold's manoeuvres.

CONCLUSIONS

Data from our prospective blinded observational study show a significantly better accuracy of ultrasound for fetal weight estimation in overweight pregnant women only as compared to Leopold's manoeuvres with a significant difference in absolute error. We did not observe significantly better accuracy of ultrasound as compared to Leopold's manoeuvres in normal weight women. Further research is needed to analyse the situation in normal weight women.

Ultrasound versus Clinical Examination to Estimate Fetal Weight at Term

Introduction At term, fetal weight estimation is an important factor for decisions about the delivery mode and the timing of labor induction. This study aimed to compare the accuracy of abdominal palpation with that of ultrasound performed by different examiners to estimate fetal weight. The study investigated whether differences in the examiners' training affected fetal weight estimates. The accuracy of the weight estimates made for fetuses with extreme birth weights was also evaluated. Finally, the accuracy of Johnson's method and of Insler and Bernstein's formula for estimating fetal weight were compared with the other two methods. Methods This prospective study included singleton pregnancies between 37 weeks of gestation and 12 days post-term planned for vaginal delivery or cesarean section. Ultrasound and abdominal palpation using Leopold's maneuvers were performed by examiners with different levels of professional experience. Fetal weight was additionally estimated using Insler and Bernstein's formula and Johnson's method. Statistical analysis calculated the accuracy of fetal weight estimates for the different examiners and the four methods. Results A total of 204 women were included in the analysis. Trained ultrasound examiners were most accurate when estimating fetal weight compared with all other examiners. The comparison of all four methods showed that fetal weight was assessed most accurately with ultrasound. No learning curve could be established. BMI and advanced gestational age affected the accuracy of the estimated weight. The analysis showed that a greater deviation between estimated weight and actual weight occurred with all four methods for fetuses at either end of the extremes of fetal weight, i.e., with very low or very high birth weights. Conclusion Fetal weight should be estimated using ultrasound. A good ultrasound training is essential.

Correlation of ultrasonographic estimated fetal weight with actual birth weight in a tertiary hospital in Lagos, Nigeria

BACKGROUND

Sonographic fetal weight estimation is an important component of antenatal care.

AIM

To sonographically estimate fetal weight at term and to compare estimated with actual birth weights to determine the validity of estimated fetal weights.

SUBJECTS AND METHODS

In the prospective study, a convenience sample of 282 women was recruited. Ethical approval and informed consent of patients were obtained. An experienced sonographer estimated fetal weights by measuring BPD, HC, AC and FL using a scanner with Hadlock 3 weight estimation model. Actual birth weights were measured with a Crown weighing scale by a midwife. Data was analyzed with SPSS software version 17.0 while descriptive and inferential statistics were used to interpret results. Results were tested at error level set at p≤ 0.05.

RESULTS

Mean estimated and actual birth weights were 3378±40g and 3393±60g respectively. Difference between the two means was not significant. Eleven percent of fetuses were sonographically estimated to be microsomic while 14.5% were microsomic at birth; 12.1% were sonographically estimated to be macrosomic but 15.2% were macrosomic at birth. Most macrosomic fetuses were delivered through cesarean section(CS) and fetal weights increased with maternal age and parity.

CONCLUSION

Sonographically estimated fetal weight using Hadlock 3 weight estimation model without validation correlated positively with actual birth weight in a Nigerian population.

The utility of ultrasound surveillance of fluid and growth in obese women

OBJECTIVE

The purpose of this study was to evaluate the utility of ultrasound surveillance in obese women.

STUDY DESIGN

This is a retrospective cohort of all obese women who underwent sonography at a single center from 2005-2013. Inclusion criteria were body mass index ≥30 kg/m(2), singleton, ≥1 ultrasound scan performed at <20 weeks of gestation, and ≥1 ultrasound scan performed at ≥24 weeks of gestation. Pregnancies with medical complications, fetal anomalies, or preterm premature rupture of membranes were excluded. Outcomes that were considered were small for gestational age, large for gestational age (LGA), macrosomia, oligohydramnios, and polyhydramnios. We calculated the number needed to screen (NNS) and 95% confidence interval (CI) for scans that were performed during 3 gestational age ranges (24-31 weeks 6 days, 32-35 weeks 6 days, and ≥36 weeks).

RESULTS

Two thousand two sonograms were performed in 1164 obese women at ≥24 weeks of gestation. Small for gestational age was diagnosed in 59 pregnancies (5.1%); 7 pregnancies (0.6%) were diagnosed at <32 weeks of gestation (NNS, 159; 95% CI, 69-490). LGA was diagnosed in 38 cases (3.3%); only 1 case was identified at <32 weeks of gestation and was not LGA at birth. For every 29 (95% CI, 19-46) scans performed at >36 weeks of gestation, 1 case of macrosomia was identified. Amniotic fluid abnormalities were diagnosed in 44 pregnancies (3.8%; oligohydramnios, 19; polyhydramnios, 25); 34.1% abnormalities were diagnosed at <32 weeks of gestation (NNS: oligohydramnios, 113; 95% CI, 55-282 for oligohydramnios; polyhydramnios, 100; 95% CI, 50-230). At ≥36 weeks of gestation, 7 (95% CI, 6-8) scans were needed to diagnose any fluid or growth abnormality.

CONCLUSION

In obese women without comorbidities, few sonographic diagnoses of amniotic fluid or fetal growth abnormalities are made at <32 weeks of gestation. Therefore, if a policy of serial sonographic surveillance is used, we suggest ultrasound scans for fluid and growth in obese women to begin at ≥32 weeks of gestation.

Clinical estimation of fetal weight: is accuracy acquired with professional experience?

OBJECTIVE

This study was conducted in order to determine whether experience and type of obstetrical profession improves the accuracy in the clinical estimation of fetal weight among obstetricians and midwives in the delivery room.

METHODS

Four groups of professionals in the delivery room clinically estimated the fetal weight in 236 parturients in active labor. Obstetric parameters such as gravidity, parity, gestational age, body mass index, amniotomy, station and cervical dilatation were recorded. Fetal weight estimations were compared with the actual birth weight after delivery.

RESULTS

The mean error rate of fetal weight estimation by attending obstetricians, residents, experienced and junior midwives was 7.9 ± 8.8, 8.0 ± 8.4, 7.8 ± 6.3 and 8.5 ± 6.8%, respectively. Error rates of the 4 groups of examiners were similar, although it was increased in all subgroups when estimating birth weights <2,500 and >4,000 g. Major discrepancies of fetal weight estimation (>10% of the actual fetal birth weight) occurred in 27.2, 28.9, 31.9 and 34.7% by attending obstetricians, residents, experienced and junior midwives, respectively.

CONCLUSIONS

We found no additional value for experience and type of obstetrical training in the accuracy of clinical fetal weight estimation.

[Obstetrical care in gestational diabetes and management of preterm labor]

OBJECTIVES

Search for data necessary to elaborate recommendations for obstetrical care in gestational diabetes and management of preterm labor.

METHODS

Systematic review of the literature and levels of evidence.

RESULTS

In case of gestational diabetes and in the absence of disease or other risk factor associated, there is no evidence to support a systematic rate of clinical follow up different from other pregnancy. The relevance of ultrasound estimates of fetal weight is limited. No formula is superior to others or to the simple measurement of abdominal circumference for the prediction of macrosomia (EL3). The usefulness of the research septal hypertrophy is not demonstrated (EL4). The systematic application of umbilical Doppler has no proven benefits in the absence of growth restriction or hypertension associated (EL4). Monthly ultrasound monitoring of the fetus can be proposed for diabetics on insulin or poorly controlled. In cases of gestational diabetes controlled by diet, cardiotocography of fetal heart rate has not proven useful. In poorly controlled diabetes and/or on insulin, the registration may be discussed taking into account other risk factors associated (EL4). A weekly recording of fetal heart rate is often recommended in case of type 2 diabetes discovered during pregnancy. In case of preterm labor, calcium channel blockers and oxytocin antagonists can be used without specific precautions. The risk of using beta-adrenergic outweighs the benefit. Administration of corticosteroid can be done under glycemic control, with insulin therapy if necessary. Screening test for gestational diabetes should not be performed within few days after last steroid injection.

Comparison of abdominal palpation, Johnson's technique and ultrasound in the estimation of fetal weight in Northern Iran

OBJECTIVES

to assess the accuracy of abdominal palpation, Johnson's technique and ultrasound in the estimation of fetal weight (EFW).

DESIGN, SETTING AND PARTICIPANTS

174 pregnant women were recruited at random in a large teaching hospital in Iran. Fetal weight was estimated by palpation and Johnson's technique at the time of admission by one qualified midwife, and then estimated by ultrasound by one radiologist. After birth, all newborns were weighed using the same scale.

FINDINGS

a significant correlation was found between EFW by ultrasound, palpation and Johnson's technique and actual birth weight. The differences between EFW by palpation, ultrasound and Johnson's technique and actual birth weight were significant for small-for-gestational-age fetuses (p<0.05, p<0.01 and p<0.001, respectively), but not for appropriate-for-gestational-age fetuses. These differences were significant for ultrasound (p<0.001) and palpation (p<0.05) in large-for-gestational-age fetuses. The sensitivity of ultrasound for EFW of low-birthweight fetuses (72.2%) and the sensitivity of Johnson's technique for EFW of normal-weight and macrosomic fetuses (97.3% and 75%, respectively) appeared to be higher than the sensitivities of the other methods.

CONCLUSION

palpation and Johnson's technique can be used as alternatives to ultrasound for EFW, particularly if the measurements are taken by experienced, skilled personnel.

Clinical estimation of fetal weight and the Hawthorne effect

OBJECTIVE

The Hawthorne effect refers to improvement in performance solely due to the subject's knowledge that he or she is being studied. We sought to determine if an obstetrician's clinical estimation of fetal weight (EFW) is influenced by the Hawthorne effect seen in some clinical trials.

STUDY DESIGN

We compared obstetricians' clinical EFW's obtained during a study period to those obtained prior to the study period in one institution. We included any patient presenting at > or =37 weeks gestation. We excluded multiple pregnancies and patients with a recent sonographic EFW.

RESULTS

There was no difference in regards to the proportion of EFW's within 10% of the birthweight (67.9% vs. 68.5%, p=.91), the mean absolute difference of EFW-birthweight (282+/-227 g vs. 285+/-232 g, p=.88), or the mean absolute percent error (8.5+/-7.4% vs. 8.6+/-7.2%, p=.96). We also could not find any Hawthorne effect when we excluded resident physicians' EFW's and when we analyzed the subgroup of newborns with a birth weight > or =4000 g.

CONCLUSION

An obstetrician's knowledge that he or she is being studied is unlikely to improve clinical EFW accuracy. Published clinical EFW accuracies are likely to be similar to those obtained in clinical practice.

Obstetric management in gestational diabetes

Reviewing the areas of controversy related to the obstetric management of women with GDM, we are unfortunately unable to provide significant refinement of the recommendations agreed upon after the Fourth International Workshop-Conference due to the lack of properly controlled and powered clinical studies in this area since 1997. In the area of the need for antenatal fetal surveillance in women with milder degrees of GDM, we may be able to draw indirect conclusions from ongoing cohort studies that will include large numbers of women. In the area of optimal timing and mode of delivery to avoid fetal injury, large well-controlled prospective studies do not currently exist and are urgently needed. In addition, refinement of fetal and pelvic imaging techniques to more accurately identify the maternal-fetal pairs most likely to benefit from avoiding vaginal delivery, and the more widespread availability of these technologies, may also prove to be of benefit in the obstetric management of women with GDM.

Clinical and ultrasound estimation of birth weight prior to induction of labor at term

OBJECTIVES

To assess and compare the accuracy of clinical and sonographic fetal weight estimation in predicting birth weight prior to induction of labor.

METHODS

In a prospective study of 262 women immediately prior to induction of labor, the fetal weight was estimated clinically by both the doctor (DR EFW) and the woman herself (WM EFW). A transabdominal scan was then performed to estimate the fetal weight sonographically using two different formulae-Shepard (SHEP EFW) and Hadlock (HAD EFW). The four estimated fetal weights were compared with the actual birth weight.

RESULTS

The mean percentage error was - 1.9 +/- 9.3% for DR EFW, - 3.4 +/- 12.6% for WM EFW, - 2.3 +/- 11.6% for SHEP EFW and - 7.6 +/- 10.6% for HAD EFW. All four EFWs were significantly different from birth weight (t = - 4.7, - 5.5, - 3.5 and - 11.4, respectively, all P < 0.01). The corresponding proportion of the EFWs which were within 10% of birth weight were 71%, 59%, 62% and 42%, respectively. The sensitivity and specificity of detecting a fetus weighing < 3000 g were 56% and 98% for DR EFW, 90% and 89% for WM EFW, 93% and 83% for SHEP EFW and 100% and 76% for HAD EFW. The corresponding values for detecting a fetus weighing > 4000 g were 16% and 99%, 29% and 96%, 48% and 92% and 40% and 94%, respectively.

CONCLUSIONS

Although, in general, clinical estimates of birth weight perform favorably compared with ultrasonographic estimates, ultrasound immediately prior to labor is more accurate at predicting the low- or high-birth-weight fetus.