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.

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.

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 formulas, mother's opinion and ultrasound in predicting birth weight

CONTEXT AND OBJECTIVE

Accurate fetal weight estimation is important for labor and delivery management. So far, there has not been any conclusive evidence to indicate that any technique for fetal weight estimation is superior to any other. Clinical formulas for fetal weight estimation are easy to use but have not been extensively studied in the literature. This study aimed to evaluate the accuracy of clinical formulas for fetal weight estimation compared to maternal and ultrasound estimates.

DESIGN AND SETTING

Prospective study involving 100 full-term, cephalic, singleton pregnancies delivered within three days of fetal weight estimation. The setting was a tertiary public teaching hospital in São Paulo, Brazil.

METHODS

Upon admission, the mother's opinion about fetal weight was recorded. Symphyseal-fundal height and abdominal girth were measured and two formulas were used to calculate fetal weight. An ultrasound scan was then performed by a specialist to estimate fetal weight. The four estimates were compared with the birth weight. The accuracy of the estimates was assessed by calculating the percentage that was within 10% of actual birth weight for each method. The chi-squared test was used for comparisons and p < 0.05 was considered significant.

RESULTS

The birth weight was correctly estimated (+/- 10%) in 59%, 57%, 61%, and 65% of the cases using the mother's estimate, two clinical formulas, and ultrasound estimate, respectively. The accuracy of the four methods did not differ significantly.

CONCLUSION

Clinical formulas for fetal weight prediction are as accurate as maternal and ultrasound estimates.

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.

Estimation of fetal weight before and after amniotomy in the laboring gravid woman

OBJECTIVE

This study was undertaken to search for differences between fetal weights estimated both ultrasonographically and clinically before and after amniotomy in laboring gravid women.

STUDY DESIGN

Estimates of fetal weight (ultrasonographic and clinical) were obtained for laboring gravid women before and after amniotomy. These estimates were compared with actual birth weights determined post partum.

RESULTS

One hundred sixty-two patients completed the study protocol. Comparisons made with unpaired Student t test analyses demonstrated a difference (P <.001) between ultrasonographically estimated fetal weights before and after amniotomy. Simple regression analysis showed a correlation between both ultrasonographic and clinical estimates of fetal weight and actual birth weights before and after amniotomy, with postamniotomy clinical estimates having the strongest correlation (ultrasonographic preamniotomy estimate, R = 0.717; ultrasonographic postamniotomy estimate, R = 0.630; clinical preamniotomy estimate, R = 0.742; and clinical postamniotomy estimate, R = 0.788). Of all ultrasonographic parameters measured, preamniotomy abdominal circumference correlated best with actual birth weight (R = 0.730).

CONCLUSION

Clinical estimates of fetal weight after amniotomy correlated well with actual birth weights. Preamniotomy abdominal circumference was the ultrasonographic parameter best for prediction of actual birth weight. Maternal weight affected clinical but not ultrasonographic estimates of fetal weight in this study. However, clinical estimates of fetal weight were actually superior to ultrasonographic estimates of fetal weight in this study.

Estimating fetal weight in the management of macrosomia

The purpose of this review is to examine the evidence that, including estimates of fetal macrosomia in patient care, will decrease adverse perinatal outcomes. A literature search for the years 1980 to 1999 was used. Shoulder dystocia and brachial plexus injuries occur more often in macrosomic than in non-macrosomic neonates. However, 26 to 58 percent of shoulder dystocias and 24 to 44 percent of brachial plexus injuries occur to babies weighing less than 4000 gm. Persistence of impairment is extremely rare. Neither historical nor clinical factors have strong positive predictive values for macrosomia. From 15 to 81 percent of the babies predicted to be macrosomic are confirmed by birth weight. Of babies determined to be macrosomic at birth, only 50 to 100 percent were successfully predicted. Shoulder dystocia and brachial plexus injuries are unpredictable events. Available evidence suggests that planned interventions based on estimates of fetal weight do not reduce the incidence of shoulder dystocia and do not decrease adverse outcomes attributable to fetal macrosomia.

Relationship between fetal femur diaphysis length and neonatal crown-heel length: the effect of race

OBJECTIVE

To determine whether racial differences affect the relationship between the fetal femur diaphysis length and the neonatal crown-heel length.

DESIGN

A prospective study in a teaching hospital with a multiracial population.

SUBJECTS

Four hundred and fifty pregnant women (150 Malays, 150 Chinese and 150 Indians) who delivered live infants.

METHODS

Ultrasound scan measurement of the fetal femur diaphysis length was carried out within 48 h of delivery in all cases. The relationship between the neonatal crown-heel length and the femur diaphysis length was obtained by regression using the method of least squares. Dummy or indicator variables were used to determine the effect of race on the relationship.

RESULTS

The relationship between the neonatal crown-heel length and the femur diaphysis length in all three races was well described by a linear model but a quadratic model described the relationship better. There was no significant difference in relationship of the neonatal crown-heel length and the femur diaphysis length between the Malay and Chinese populations, but the relationship in the Indian population was significantly different was from both the Chinese and Malay. For a given femur diaphysis length, the crown-heel length of the Indian population was found on average to be 1.1 cm shorter than the crown-heel length of the Malay and Chinese populations.

CONCLUSION

Differences in fetal body proportions exist between some races. The longer femur diaphysis length noted in certain races does not necessarily imply that the corresponding crown-heel length is longer. These inter-racial differences may increase the error of fetal weight and length estimates if formulae, which have been derived from samples racially dissimilar to that of the target population are used.

A comparison between ultrasound and clinical methods for predicting fetal weight

Fetal weight prediction by different methods were compared. Those methods were ultrasound fetal weight estimations using Campbell, Warsof and Hadlock equations, and clinical subjective estimation by experienced obstetricians, as well as clinical objective studies (Zayed's equation). We evaluated 523 Jordanian (Arabic) patients in labour. Our results shows that ultrasound equation provides the highest accuracy in predicting fetal weight. In this study Hadlock's equation was more precise than the other equations. There is still a place for clinical fetal weight estimation, especially if objection methods are used.

Clinical and ultrasound prediction of macrosomia in diabetic pregnancy

OBJECTIVE

To study prospectively the prediction power, at different gestations, of clinical and ultrasound measurements for fetal size in diabetic pregnancy.

SETTING

A large combined obstetric diabetic clinic in a teaching hospital.

PARTICIPANTS

One hundred and eighty-one pregnancies in which women had scans at least two of three specific time points and who were delivered of singletons after 34 weeks: 73% were pre-gestational insulin-dependent diabetics, the others were pre-gestational White class A or gestational diabetics.

INTERVENTIONS

Clinical estimates of fundal height and fetal size and ultrasound estimates of abdominal circumference and head circumference were routinely carried out at gestational ages of 28, 34 and 38 weeks or before delivery.

MAIN OUTCOME MEASURES

Standardised birthweight, corrected for gestation and parity. The relation with clinical and ultrasound measurements was investigated using multiple linear regression and the capability of the measurements to predict macrosomic births (> 95th centile of normals) using receiver-operator characteristic curves.

RESULTS

All measurements are poor predictors of eventual standardised birthweight. Prediction improves with closeness to delivery. Prediction is significantly improved by adding ultrasound to clinical information, but at 34 weeks or later this only contributes 8% of the variance. There is no difference in the prediction power for macrosomia between clinical and ultrasound measurements.

CONCLUSIONS

Even regular serial scanning and clinical examination will not always diagnose the macrosomic fetus in diabetic pregnancy. In our hands, clinical examination is as predictive as ultrasound measurements. Ultrasound does add to clinical prediction power but only to a small extent. Ultrasound should be used in a selected way, as defined by clinical findings, and with recognition and understanding of the errors and biases involved.

Fetal macrosomia: does antenatal prediction affect delivery route and birth outcome?

OBJECTIVE

Our purpose was to determine whether clinical or ultrasonographic prediction of fetal macrosomia influences subsequent delivery route and birth outcome in a clinical setting where macrosomia is not considered an indication for cesarean delivery.

STUDY DESIGN

The hospital records of 504 patients delivered of infants weighing > or = 4200 gm between October 1989 and March 1994 were reviewed. Statistical comparisons were made between patients in whom fetal macrosomia was predicted before delivery (n = 102) and those in whom it was not (n = 402). Cesarean delivery, shoulder dystocia, and birth trauma rates were the variables of interest.

RESULTS

Cesarean sections were performed in 52% of the "predicted" group deliveries and in 30% of the "not predicted" group (p < 0.01). The increased cesarean delivery rate in the predicted group appeared to be related to an increased incidence of labor inductions (42.5% vs 26.6%, p = 0.005) and a greater proportion of failed inductions. The proportion of patients delivered by cesarean section without a trial of labor was similar in the predicted and not predicted groups (14.7% vs 10.2%, p = 0.21). There was no significant differences in the incidence of shoulder dystocia or the occurrence of birth trauma.

CONCLUSIONS

The antenatal prediction of fetal macrosomia is associated with a marked increase in cesarean deliveries without a significant reduction in the incidence of shoulder dystocia or fetal injury. Ultrasonography and labor induction for patients at risk for fetal macrosomia should be discouraged.