A review of sonographic estimate of fetal weight: Vagaries of accuracy

To know or not to know: Effect of third-trimester sonographic fetal weight estimation on outcomes of large-for-gestational age neonates

OBJECTIVE

The aim of the present study was to evaluate the impact of late third-trimester sonographic estimation of large for gestational age fetuses on pregnancy management and selected fetal and maternal adverse outcomes.

METHODS

A retrospective cohort study was conducted in a tertiary, university-affiliated medical center between 2015 and 2019. All singleton large-for-gestational-age neonates born during this period were included. The cohort was divided into two groups: neonates for whom fetal weight was estimated on late third trimester (<14 days before delivery) sonography and neonates with no recent fetal weight estimation. The groups were compared for pregnancy management strategies, rates of labor induction, cesarean deliveries, and maternal and neonatal outcomes.

RESULTS

A total of 1712 neonates were included in the study, among whom 791 (46.2%) had a late third-trimester fetal weight estimation (study group) and 921 (53.8%) did not (control group). Compared to the control group, the study group was characterized by higher rates of maternal primiparity (24.20% vs 19.20%, P = 0.013), higher maternal body mass index (26.0 ± 6.2 kg/m2 vs 24.7 ± 4.5 kg/m2, P = 0.002), more inductions of labor (29.84% vs 16.40%, P < 0.001) and cesarean deliveries (31.0% vs 19.97%, P < 0.001). There were no clinical differences in neonatal birth weight (4041 ± 256 g vs 3984 264 g, P < 0.001) and no significant differences between other neonatal outcomes, as rates of admission to the neonatal intensive care unit, jaundice, hypoglycemia, and shoulder dystocia.

CONCLUSION

Late third-trimester sonographic fetal weight estimation is associated with a higher rate of labor induction and planned and intrapartum cesarean deliveries. In this retrospective cohort study, those interventions did not lead to reduction in maternal or neonatal adverse outcomes.

Performance of fetal ultrasound and magnetic resonance imaging in predicting birthweight according to the test-to-delivery interval: A cohort study

OBJECTIVE

To assess the influence of the test-to-delivery interval (TDI) on the performance of ultrasound (US) and magnetic resonance imaging (MRI) for predicting birthweight (BW).

STUDY DESIGN

This is a secondary analysis of a prospective, single center, blinded cohort study that compared MRI and US for the prediction of BW ≥ 95th percentile in singleton pregnancies. Patients that were included in the initial study underwent US and MRI for estimation of fetal weight between 36 + 0/7 and 36 + 6/7 weeks of gestation (WG). The primary outcome of the current study was to report the changes of US and MRI sensitivity and specificity in the prediction of BW > 95th percentile, BW > 90th percentile, BW < 10th percentile, and BW < 5th percentile, according to the TDI. The secondary outcome was to represent the performance of both tools in the prediction of BW > 90th percentile when TDI is<2 weeks, between 2 and 4 weeks, and>4 weeks. Receiver operating characteristic (ROC) curves were constructed accordingly.

RESULTS

2378 patients were eligible for final analysis. For the prediction of BW > 95th or 90th percentile, the sensitivity of MRI remains high until 2 weeks, and it decreases slowly between 2 and 4 weeks, in contrast to the sensitivity of US which decreases rapidly 2 weeks after examination (p < 0.001). For the prediction of BW < 10th or 5th percentile, the sensitivity of both tools decreases in parallel between 1 and 2 weeks. The specificities of both tools remain high from examination till delivery. These findings are reproducible with the use of the antenatal customized and the postnatal national growth charts.

CONCLUSION

The performance of MRI in the prediction of BW, especially in large-for-gestational age, is maximal when delivery occurs within two weeks of the examination, decreasing slightly thereafter, in contrast with the performance of US which decreases drastically over time.

Accuracy of the sonographic determination of estimated fetal weight in anhydramnios

OBJECTIVE

To determine whether the presence of anhydramnios significantly influences the sonographic estimated fetal weight (EFW) compared to a matched cohort with normal amniotic fluid volume.

METHODS

The study sample of this retrospective case-control study consisted of 114 pregnant women who presented to a Tertiary Perinatal Clinic between 2015 and 2020. 57 of them presented with an anhydramnios and a matched cohort of 57 women with normal amniotic fluid volume. At time of admission, gestational age varied between 22 + 4 and 42 + 6 weeks of pregnancy. All women underwent detailed ultrasound assessment for EFW and amniotic fluid index. To determine EFW Hadlock's estimation formula I was used which is based on measurements of biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC) and femur length (FL). The EFW was compared with the weight at delivery. The maximum time interval between measurement and delivery was 5 days.

RESULTS

There was neither a significant difference between the case and control group with regard to gestational age at ultrasound in days (median 249 days and 246 days, p = 0.97), nor to gestational age at birth (median 249 days and 247 days, p = 0.98). Concerning the newborns parameters, the body length at birth was not significantly different between the case and control group in centimeters (cm) (median 47 cm and 47 cm, p = 0.79). EFW in gram (g) was lower than birth weight in both groups and did not differ significantly between case and control group (estimated weight median 2247 g and 2421 g, p = 0.46; birth weight median 2440 g and 2475 g, p = 0.47). The difference between EFW and birth weight in percent (%) did not differ between the case and control group (median - 3.9% and - 5.6%, p = 0.70). The maternal parameters showed that the patients in the case group were younger (median 31 years and 38 years p = 0.20) and had a significantly higher body mass index (BMI) (median 27.3 kg/m2 vs 22.0 kg/m2, < 0.001) compared to the control group.

CONCLUSION

Our study shows for the first time that EFW in women with anhydramnios can be determined sonographically just as accurately as in a matched cohort with normal amniotic fluid volume. A reliable estimation of fetal weight is crucial for optimal assessment of the newborns prognosis and counseling of the parents especially when advising women in the early weeks of pregnancy at the limit of viability.

Perinatal and Maternal Outcomes According to the Accurate Term Antepartum Ultrasound Estimation of Extreme Fetal Weights

(1) Background: The accuracy of ultrasound estimation of fetal weight (EFW) at term may be useful in addressing obstetric complications since birth weight (BW) is a parameter that represents an important prognostic factor for perinatal and maternal morbidity. (2) Methods: In a retrospective cohort study of 2156 women with a singleton pregnancy, it is verified whether or not perinatal and maternal morbidity differs between extreme BWs estimated at term by ultrasound within the seven days prior to birth with Accurate EFW (difference < 10% between EFW and BW) and those with Non-Accurate EFW (difference ≥ 10% between EFW and BW). (3) Results: Significantly worse perinatal outcomes (according to different variables such as higher rate of arterial pH at birth < 7.20, higher rate of 1-min Apgar < 7, higher rate of 5-min Apgar < 7, higher grade of neonatal resuscitation and need for admission to the neonatal care unit) were found for extreme BW estimated by antepartum ultrasounds with Non-Accurate EFW compared with those with Accurate EFW. This was the case when extreme BWs were compared according to percentile distribution by sex and gestational age following the national reference growth charts (small for gestational age and large for gestational age), and when they were compared according to weight range (low birth weight and high birth weight). (4) Conclusions: Clinicians should make a greater effort when performing EFW by ultrasound at term in cases of suspected extreme fetal weights, and need to take an increasingly prudent approach to its management.

Is accuracy of estimated fetal weight improved by better image quality scores?

OBJECTIVE

To assess in a group of ultrasound operators of various levels of experience the predictive value of systematic quality scoring to assess estimated fetal weight (EFW) validity.

METHODS

Screenshots, sonographer experience, and neonate birth weight were collected for 131 ultrasound examinations in the 7 days before birth. The difference (EFW error) between projected birth weight (EFW + [30 g × interval in days to birth]) and actual birth weight was then assessed (absolute value). Three senior sonographers rated all the screenshots (International Society of Ultrasound in Obstetrics and Gynecology 16-point score for image quality) and interobserver reproducibility was assessed concomitantly. The impact of the score on EFW accuracy was then assessed (univariate analysis). Receiver operating characteristic curves allowed us to assess the score's positive predictive value (PPV) for accurate EFW.

RESULTS

Mean birth weight was 2998 ± 954 g and mean EFW error was 8.6% ± 7.1%. Both the sonographer's experience and score significantly impacted the EFW error (P < 0.05). The PPVs of systematic image scores for identifying an EFW error greater than 10% and greater than 15% were appropriate for clinical use (areas under the curve 0.61 and 0.70, respectively). Score reproducibility was modest.

CONCLUSION

Low image scores and limited ultrasound expertise are associated with an increased risk of inaccurate EFW.

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

OBJECTIVE

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

METHOD

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

RESULT

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

CONCLUSION

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

Shoulder Dystocia: Challenging Basic Assumptions

Most of our knowledge pertaining to this obstetric emergency has emanated from case reports and retrospective studies that have subsequently resulted in empirical management protocols. This article has identified the existence of large gaps in our clinical knowledge base regarding the prevention and resolution of shoulder dystocia, as well as its long-term sequelae. We have attempted to challenge current recommendations regarding whether prophylactic cesarean delivery should be performed based on estimated fetal weight alone or a prior history of shoulder dystocia, shoulder dystocia management techniques, what defines "excessive" traction, and the role of simulation training for all clinicians.

Validity of two-dimensional ultrasound for determining extreme foetal weights to term

The aim of this study was to assess the validity of ultrasound carried out within seven days prior to birth at term for the calculation of full term estimated foetal weight (EFW) in order to diagnose extreme foetal weight, performed using a single-center retrospective cohort study of 2500 pregnant women. Ultrasound calculations of EFW with a standard error of less than 10% showed an accuracy ratio of 75.1% for the total sample. This percentage was similar for appropriate for gestational age (78.6%) and normal foetal weights (77.5%) but decreased significantly (p < .01) in the case of extreme foetal weights. The simple error increased in both the high and low EFWs, taking on positive values for the low weights and negative values for the high weights. As for the percentage error values, there was a tendency for positive errors for low weights and negative errors for high weights; this led to a tendency to overestimate low foetal weights and underestimate high foetal weights.IMPACT STATEMENTWhat is already known on this subject? Two-dimensional ultrasound is currently the principal tool used in obstetrics to evaluate foetal growth, mainly through the calculation of EFW. Foetal weight represents an important prognostic factor in perinatal results, with a greater risk of adverse effects in cases of extreme foetal weights. In this sense, there are few studies that assess the validity of EFW calculations focussing on extreme foetal weights to term.What do the results of this study add? The ultrasound estimates of EFW with an error lower than 10% in the seven days prior to birth showed an accuracy ratio of 75.1% for the total sample. This percentage was similar to appropriate for gestational age weights (78.6%) and of normal weights (77.5%), but decreased significantly (p < .01) in the case of extreme foetal weights: small for gestational age (52.1%), large for gestational age (68.2%), microsomia (49.1%), and macrosomia (61%). Likewise, we found high specificity and low sensitivity for ultrasound diagnosis of extreme foetal weights.What are the implications of these findings for clinical practice and/or future research? The validity of ultrasound EFW is influenced by extreme foetal weights, with a tendency to overestimate low weights and underestimate high weights, which represents a clinically important finding.

Accuracy of ultrasound in estimating fetal weight in New Zealand

Introduction

Ultrasound estimation of fetal weight is an important factor guiding antenatal management. We aimed to review the accuracy of ultrasound in predicting fetal weight and birthweight category and identify influencing factors.

Methods

We performed a retrospective study of term pregnant women who underwent ultrasound within 7 days of delivery at National Women's Health between January 2019 and January 2020. Stillbirths, major fetal anomalies and multiple pregnancies were excluded. Estimated fetal weight (EFW) was calculated using Hadlock formula and compared with birthweights. We evaluated change in weight categories due to these errors.

Results

Of 560 fetuses included, three quarters (n = 425, 76%) of EFWs were within 10% of birthweight. 135 fetuses had EFWs either less than 90% (n = 19) or greater than 110% (n = 116). Fetuses with EFW < 90% had longer times between scanning and delivery, lower EFW and higher maternal BMI. Fetuses with EFW > 110% were associated with higher EFW, later gestational age and older maternal age. US incorrectly estimated 71 (12.7%) fetal birthweight categories. Underestimated weight category (8.9%) was associated with higher maternal BMI.

Discussion

Inaccurate EFWs were more common at the extremes of fetal weight. A significant association was underestimation birthweight in mothers with increased BMI, who are at increased risk for perinatal and surgical complications.

Conclusion

Our accuracy of 76% correctly predicted EFWs compares favourably with previous studies. Clinicians and sonographers should be aware of the increased risk for inaccurate categorisation of fetuses at the extremes of EFW and in mothers with increased BMI.

Predicting fetal weight by three-dimensional limb volume ultrasound (AVol/TVol) and abdominal circumference

BACKGROUND

Fetal weight is an important parameter to ensure maternal and child safety. The purpose of this study was to use three-dimensional (3D) limb volume ultrasound combined with fetal abdominal circumference (AC) measurement to establish a model to predict fetal weight and evaluate its efficiency.

METHODS

A total of 211 participants with single pregnancy (28-42 weeks) were selected between September 2017 and December 2018 in the Beijing Obstetrics and Gynecology Hospital of Capital Medical University. The upper arm (AVol)/thigh volume (TVol) of fetuses was measured by the 3D limb volume technique. Fetal AC was measured by two-dimensional ultrasound. Nine cases were excluded due to incomplete information or the interval between examination and delivery >7 days. The enrolled 202 participants were divided into a model group (134 cases, 70%) and a verification group (68 cases, 30%) by mechanical sampling method. The linear relationship between limb volume and fetal weight was evaluated using Pearson Chi-squared test. The prediction model formula was established by multivariate regression with data from the model group. Accuracy of the model formula was evaluated with verification group data and compared with traditional formulas (Hadlock, Lee2009, and INTERGROWTH-21st) by paired t-test and residual analysis. Receiver operating characteristic curves were generated to predict macrosomia.

RESULTS

AC, AVol, and TVol were linearly related to fetal weight. Pearson correlation coefficient was 0.866, 0.862, and 0.910, respectively. The prediction model based on AVol/TVol and AC was established as follows: Y = -481.965 + 12.194TVol + 15.358AVol + 67.998AC, R2adj = 0.868. The scatter plot showed that when birth weight fluctuated by 5% (i.e., 95% to 105%), the difference between the predicted fetal weight by the model and the actual weight was small. A paired t-test showed that there was no significant difference between the predicted fetal weight and the actual birth weight (t = -1.015, P = 0.314). Moreover, the residual analysis showed that the model formula's prediction efficiency was better than the traditional formulas with a mean residual of 35,360.170. The combined model of AVol/TVol and AC was superior to the Lee2009 and INTERGROWTH-21st formulas in the diagnosis of macrosomia. Its predictive sensitivity and specificity were 87.5% and 91.7%, respectively.

CONCLUSION

Fetal weight prediction model established by semi-automatic 3D limb volume combined with AC is of high accuracy, sensitivity, and specificity. The prediction model formula shows higher predictive efficiency, especially for the diagnosis of macrosomia.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT03002246; https://clinicaltrials.gov/ct2/show/NCT03002246?recrs=e&cond=fetal&draw=8&rank=67.

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

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

Analysis of factors influencing accuracy of ultrasound-based fetal weight estimation

Context:

The primary objective of this study was to examine the impact of maternal age, parity, gestational age, fetal gender, gestational diabetes mellitus, and pregnancy-induced hypertension on the accuracy of ultrasonography-based fetal weight estimation. The secondary objective was to find the impact of a formula selection on the accuracy of fetal weight estimation.

Subjects and Methods:

The inclusion criteria were a live-birth singleton pregnancy and the last ultrasound scan to delivery interval ≤7 days. Fetal weight was estimated using the Hadlock-4 formula. To study the concurrent impact of all the factors on the accuracy, cases were divided into two subcategories based on percentage error, with ±10% as a threshold. The accuracy of Hadlock-4 formula was compared with the two Indian population-based formulas, Hiwale-1 and Hiwale-2.

Results:

In total, 184 cases were included in the study. It was observed that the systematic error in weight estimation was significantly less in the male fetuses (8.45 ± 9.34%) in comparison to the female fetuses (11.71 ± 10.34%). The combined impact of all the factors on the accuracy was found to be nonsignificant by the multivariate analysis. The Hiwale-1 (-0.59 ± 8.75%) and Hiwale-2 (-0.65 ± 8.7%) formulas had statistically significant less errors compared to the Hadlock-4 formula (11.67 ± 7.95%).

Conclusion:

All the studied clinical factors were found to have a limited impact on the overall accuracy of fetal weight estimation. However, the formula selection was found to have a significant impact on the accuracy, with the native population-based formulas being significantly more accurate.

Identification of newborns with birthweight ≥ 4,500g: Ultrasound within one- vs. two weeks of delivery

OBJECTIVE

Our objective was to compare the diagnostic characteristics of sonographic estimated fetal weight (SEFW) done within 7 versus 8-14 days before delivery for detection of fetal macrosomia (birthweight ≥ 4500 g).

STUDY DESIGN

We performed a multicenter, retrospective cohort study of all non-anomalous singletons with SEFW ≥ 4000 g by Registered Diagnostic Medical Sonographers conducted within 14 days of delivery. Cohorts were grouped by time interval between ultrasound and delivery: 0-7 days versus 8-14 days. The detection rate (DR) and false positive rate (FPR) for detection of birthweight (BW) ≥ 4500 g were compared between groups with subgroup analysis for diabetic women. Area under the receiver operator curve (AUC) was calculated to analyze all possible SEFW cutoffs within our cohort.

RESULTS

A total of 330 patients met inclusion criteria with 250 (75.8 %) having SEFW within 7 days and 80 (24.2 %) with SEFW 8-14 days prior to delivery. The rate of macrosomia was 15.1 % (N = 51). The DR for macrosomia was significantly higher when SEFW was performed within 7 days of delivery compared to 8-14 days among non-diabetic (73.0 % vs 7.1 %; p < 0.001) and diabetic women (76.5 % vs 16.7 %; p = 0.02). There was no significant change in FPR in either group. The AUC for detection of macrosomia was significantly higher when SEFW was performed within 7 days versus 8-14 days (0.89 vs 0.63; p < 0.01).

CONCLUSION

With SEFW ≥ 4000 g, the detection of BW ≥ 4500 g is significantly higher when the sonographic examination is within 7 days of birth irrespective of maternal diabetes.

Serial Third-Trimester Ultrasonography Compared With Routine Care in Uncomplicated Pregnancies: A Randomized Controlled Trial

OBJECTIVE

Among uncomplicated pregnancies, serial third-trimester ultrasound examinations identified significantly more cases with a composite of fetal growth or amniotic fluid abnormalities (27%) than did routine fundal height measurements (8%).

METHODS

Women without complications between 24 0/7 and 30 6/7 weeks of gestation were randomized (NCT0270299) to either routine care (control arm) or ultrasound examination every 4 weeks (intervention arm). The primary outcome was a composite of abnormalities of fluid volume and growth: oligohydramnios or polyhydramnios; fetal growth restriction; or large for gestational age. The secondary outcome was the presence of composite maternal or neonatal morbidity among the two groups. A total of 206 participants was needed to have 80% power to detect an increase in the primary composite outcome from 10% in control to 25% in the intervention group (baseline rate 10%; two-tailed; α=0.05; loss to follow-up 5%). All women were included in the intent-to-treat analysis. Fisher exact, χ tests, or two-sample t tests were used to assess group differences.

RESULTS

From July 11, 2016, to May 24, 2017, 852 women were screened for eligibility and 206 were randomized as follows: 102 in routine care and 104 in serial ultrasound examinations. The two groups were comparable in baseline characteristics. The primary composite outcome was significantly higher among women who were in the ultrasound examination group than the routine care group (27% vs 8%; relative risk 3.43, 95% CI 1.64-7.17); five women (95% CI 3-11) were needed to identify at least one of the composite ultrasound abnormalities. Although we were underpowered to detect a significant difference, the following secondary endpoints occurred with similar frequency in the ultrasound examination group than the routine care group: induction resulting from abnormal ultrasound examination findings (14% vs 6%), cesarean delivery in labor (5% vs 6%), and prespecified composite maternal morbidity (9% in both groups) and composite neonatal morbidity (1% vs 4%).

CONCLUSION

Among uncomplicated pregnancies between 24 0/7 and 30 6/7 weeks of gestation, serial third-trimester ultrasound examinations were significantly more likely to identify abnormalities of fetal growth or amniotic fluid than measurements of fundal height and indicated ultrasound examination. No differences in maternal and neonatal outcomes were noted, although we were underpowered for these endpoints.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, NCT02702999.

Concordance Rates Between Resident-Performed Ultrasound Measurements and Certified Sonographer Measurements

OBJECTIVES

To evaluate the accuracy of ultrasound (US) estimated fetal weight (EFW) measurement compared with neonatal birth weight when performed by residents versus certified sonographers. The hypothesis tested was that residents and certified sonographers would not differ significantly in EFW or in EFW compared with neonatal birth weight.

METHODS

A retrospective chart review of 142 inpatients from July 2010 to May 2011 was conducted. Ultrasound examinations were performed by a resident physician and a certified sonographer within 7 days after the resident. Standard US measurements obtained were head circumference, biparietal diameter, abdominal circumference, femur length, estimated gestational age, and EFW. Gestational age ranged from 20 to 39 weeks. The time from US to delivery, residency year, and birth weight were collected. Measurements were compared by paired t tests, the Wilcoxon signed rank test, and repeated-measures analysis of variance.

RESULTS

The US EFW by residents and sonographers showed excellent concordance with each other regardless of the neonatal birth weight. The resident and sonographer EFW each showed excellent concordance with the neonatal birth weight, and this concordance did not differ significantly between residents and sonographers for neonates weighing less than 1000 g (P = .61) and neonates weighing greater than or equal to 1000 to less than 2000 g (P = .93). The resident EFW (P < .05) and sonographer EFW (P < .01), however, were less than the neonatal birth weight for larger neonates (≥2000 g), but the degree of underestimation was not significantly different between residents and sonographers (P = .51).

CONCLUSIONS

Accurate EFW is critical for prenatal management. These data support the value of a dedicated month of US training in residency programs.

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSION

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

Sonographic Estimated Fetal Weight among Diabetics at ≥ 34 Weeks and Composite Neonatal Morbidity

Objectives  The objective was to assess the composite neonatal morbidity (CNM) among diabetic women with sonographic estimated fetal weight (SEFW) at 10 to 90th versus >90th percentile for gestational age (GA). Study Design  The inclusion criteria for this retrospective study were singleton pregnancies at 34 to 41 weeks, complicated by diabetes, and that had SEFW within 4 weeks of delivery. Odds ratios (ORs) with 95% confidence intervals (CI) were calculated. Results  Among the 140 cohorts that met the inclusion criteria, 72% had SEFW at 10th to 90th percentile for GA, and 28% at >90th percentile. Compared with women with diabetes with last SEFW at 10th to 90th percentile, those with estimate > 90th percentile for GA had a significantly higher rate of CNM (13 vs. 28%; OR, 2.65; 95% CI, 1.07-6.59). Among 109 diabetic women who labored, the rate of shoulder dystocia was significantly higher with SEFW at >90th percentile for GA than those at 10th to 90th percentile (25 vs. 2%; p  = 0.002); the corresponding rate of CNM was 29 versus 10% ( p  = 0.02). Conclusion  Among diabetic women with SEFW > 90th percentile for GA, CNM was significantly higher than in women with estimate at 10 to 90th percentile. Despite the increased risk of CNM, these newborns did not have long-term morbid sequela.

Neonatal Morbidity of Small- and Large-for-Gestational-Age Neonates Born at Term in Uncomplicated Pregnancies

OBJECTIVE

To compare morbidity among small-for-gestational-age (SGA; birth weight less than the 10th percentile for gestational age), appropriate-for-gestational-age (AGA; birth weight 10th to 90th percentile; reference group), and large-for-gestational-age (LGA; birth weight greater than the 90th percentile) neonates in apparently uncomplicated pregnancies at term (37 weeks of gestation or greater).

METHODS

This secondary analysis, derived from an observational obstetric cohort of 115,502 deliveries, included women with apparently uncomplicated pregnancies of nonanomalous singletons who had confirmatory ultrasound dating no later than the second trimester and who delivered between 37 0/7 and 42 6/7 weeks of gestation. We used two different composite neonatal morbidity outcomes: hypoxic composite neonatal morbidity for SGA and traumatic composite neonatal morbidity for LGA neonates. Log Poisson relative risks (RRs) with 95% CIs adjusted for potential confounding factors (nulliparity, body mass index, insurance status, and neonatal sex) were calculated.

RESULTS

Among the 63,436 women who met our inclusion criteria, SGA occurred in 7.9% (n=4,983) and LGA in 8.3% (n=5,253). Hypoxic composite neonatal morbidity was significantly higher in SGA (1.1%) compared with AGA (0.7%; adjusted RR 1.44, 95% CI 1.07-1.93) but similar between LGA (0.6%) and AGA (adjusted RR 0.84, 95% CI 0.58-1.22). Traumatic composite neonatal morbidity was significantly higher in LGA (1.9%) than AGA (1.0%; adjusted RR 1.88, 95% CI 1.51-2.34) but similar in SGA (1.3%) compared with AGA (adjusted RR 1.28, 95% CI 0.98-1.67).

CONCLUSION

Among women with uncomplicated pregnancies, hypoxic composite neonatal morbidity is more common with SGA neonates and traumatic-composite neonatal morbidity is more common with LGA neonates.

The clinical significance of an estimated fetal weight below the 10th percentile: a comparison of outcomes of <5th vs 5th-9th percentile

BACKGROUND

The association between small-for-gestational-age (birthweight <10th percentile for gestational age) and neonatal morbidity is well established. Yet, there is a paucity of data on the relationship between suspected small for gestational age (sonographic-estimated fetal weight <10th percentile) at 2 thresholds and subsequent neonatal morbidity.

OBJECTIVE

The objective of this study was to determine the relationship between sonographic-estimated fetal weight <5th percentile vs 5-9th percentile and neonatal morbidity.

STUDY DESIGN

This retrospective study involved 5 centers and included nonanomalous, singletons with sonographic-estimated fetal weight <10th percentile for gestational age who delivered from 2009-2012. Composite neonatal morbidity included respiratory distress syndrome, proven sepsis, intraventricular hemorrhage grade III or IV, necrotizing enterocolitis, thrombocytopenia, seizures, or death. Odd ratios were adjusted for center, maternal age, race, body mass index at first visit, smoking status, use of alcohol, use of drugs, and neonatal gender.

RESULTS

Of 834 women with suspected small-for-gestational-age fetuses, 513 (62%) had sonographic-estimated fetal weight <5th percentile, and 321 (38%) had sonographic-estimated fetal weight of 5-9th percentile for gestational age. At delivery, 81% of women with a suspected small-for-gestational-age fetus had a confirmed small-for-gestational-age fetus. In the group with a sonographic-estimated fetal weight <5th percentile, 59% of neonates had birthweight <5th percentile; in the group with a sonographic-estimated fetal weight 5-9th percentile, 41% had birthweight <5th percentile, and 36% had birthweight at 5-9th percentile. Neonatal intensive care unit admission differed significantly for those fetuses at <5th percentile (29%) compared with those fetuses at 5-9th percentile (15%; P<.001). The composite neonatal morbidity among the sonographic-estimated fetal weight <5th percentile group was higher than the sonographic-estimated fetal weight of 5-9th percentile group (31% vs 13%; adjusted odds ratio, 2.41; 95% confidence interval, 1.53-3.80). Similar findings were noted when the analysis was limited to sonographic-estimated fetal weight within 28 days of delivery (adjusted odds ratio, 2.22; 95% confidence interval, 1.34-3.67).

CONCLUSION

Eight of 10 suspected small-for-gestational-age fetuses had birthweight <10th percentile for gestational age; the prediction of actual birthweight was more accurate in the <5th percentile group. Neonates with sonographic-estimated fetal weight of <5th percentile were more likely to be admitted to the neonatal intensive care unit and have complications than were those neonates with sonographic-estimated fetal weight of 5-9th percentile.

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.

Longitudinal Assessment of Examiner Experience and the Accuracy of Sonographic Fetal Weight Estimation at Term

OBJECTIVES

To evaluate the influence of examiner experience on the accuracy of sonographic weight estimation and to further analyze examiners' individual learning curves.

METHODS

In this multicenter study, 4613 sonographic weight estimations performed by 18 examiners at the beginning of their ultrasound training were included. To assess the effect of experience on the accuracy of weight estimation, a multivariable mixed regression model analysis was performed, with percentage error and absolute percentage error as outcome variables and the examiner, the examiner's experience (number of examinations), birth weight, gestational age, scan-to-delivery interval, and maternal body mass index as fixed effects and the perinatal center as random intercepts. To further analyze the individual learning curves of the examiners, the cumulative summation technique was used.

RESULTS

Regression analyses showed a significant influence of the number of examinations on the accuracy of sonographic weight estimation after adjustment for the above-mentioned parameters (P < .001). A typical learning curve with improving accuracy was found until approximately 200 examinations. Between 200 and 300 examinations, the diagnostic performance started to deteriorate again, with a continuous decrease until the end of the study period. Cumulative summation charts representing individual learning curves varied greatly between different examiners.

CONCLUSIONS

These findings indicate the great importance of continuous quality control systems in sonographic weight estimation.

Small-for-gestational-age infants among uncomplicated pregnancies at term: a secondary analysis of 9 Maternal-Fetal Medicine Units Network studies

BACKGROUND

Most small (birthweight <10%) for-gestational-age cases occur at term, in uncomplicated pregnancies, and are not identified during prenatal visits as having fetal growth restriction. Hence, they do not benefit from antepartum surveillance and timed delivery. There is dismissive and disquieting opinion that small for gestational age among uncomplicated pregnancies is not associated with increased morbidities and, therefore, does not warrant improved detection. Our hypothesis was that among uncomplicated pregnancies at term, small for gestational age have significantly higher morbidity and mortality than appropriate (birthweight 10-89%) for gestational age.

OBJECTIVE

We sought to compare composite neonatal morbidity among uncomplicated term singleton pregnancies with small vs appropriate for gestational age.

STUDY DESIGN

We culled collected data from 9 completed Maternal-Fetal Medicine Units studies conducted from 1989 through 2004. All data were collected prospectively by trained staff. We excluded women who delivered <37 weeks and those with hypertension or diabetes, multiple gestation, known anomalies, and birthweight of ≥90% for gestational age. Using multivariable analysis, we compared composite neonatal morbidity, which included stillbirth and neonatal mortality between small and appropriate for gestational age. Random effect logistic regressions were used to account for study heterogeneity, with adjustment for potential confounders. We calculated adjusted odds ratios and 95% confidence intervals.

RESULTS

Of the >91,000 women enrolled in the studies, 60% (n = 50,011) met the inclusion criteria. Among the uncomplicated pregnancies, 10.8% (n = 5416) were small for gestational age. The rate of composite neonatal morbidity of 16% in small for gestational age and 10% in appropriate for gestational age persisted (adjusted odds ratio, 1.75; 95% confidence interval, 1.71-1.78). After adjustment for confounders, the following neonatal morbidities were significantly more common among term small than appropriate for gestational age: Apgar <4 at 5 minutes, respiratory distress syndrome, mechanical ventilation, necrotizing enterocolitis grade 2 or 3, and neonatal sepsis. Lastly, rate of stillbirths (3.5 vs 0.9/1000 births; adjusted odds ratio, 3.49; 95% confidence interval, 1.83-6.67) and neonatal mortality (1.1 vs 0.4/1000 births; adjusted odds ratio, 2.56; 95% confidence interval, 1.83-3.57) were significantly more common with small than appropriate for gestational age. In secondary analyses the composite neonatal morbidity among newborns at <5% and at 5-9% was significantly higher than appropriate for gestational age. Lastly, in subgroup analyses of women who delivered at 37.0-38.6 weeks or at ≥39.0 weeks, the increased rate of composite neonatal morbidity, stillbirth, and neonatal mortality among small for gestational age persisted.

CONCLUSION

Among uncomplicated pregnancies at term, small- compared to appropriate-for-gestational-age newborns have a significantly higher likelihood of composite neonatal morbidity, stillbirth, and neonatal mortality. A large multicenter trial is warranted to determine if improved detection of small for gestational age among uncomplicated pregnancies can mitigate morbidities and mortality, without disproportionate interventions and iatrogenic complications.

Uncomplicated Pregnancies and Ultrasounds for Fetal Growth Restriction: A Pilot Randomized Clinical Trial

Objective The purpose of this multicenter pilot study was to determine the feasibility of randomizing uncomplicated pregnancies (UPs) to have third trimester ultrasonographic exams (USE) versus routine prenatal care (RPNC) to improve the detection of small for gestational age (SGA; birth weight < 10% for GA). Material and Methods At three referral centers, 50 UPs were randomized after gestational diabetes was ruled out. Women needed to screen, consenting, and loss to follow-up was ascertained, as was the detection rate of SGA in the two groups. Results During the study period at the three centers, there were 7,680 births, of which 64% were uncomplicated. Of the 234 women approached for randomization, 36% declined. We recruited 149 women and had follow-up delivery data on 97%. The antenatal detection rate of SGA in the intervention group was 67% (95% confidence intervals 31-91%) and 9% (0.5-43%) in control. Conclusion The pilot study provides feasibility data for a multicenter randomized clinical trial to determine if third trimester USE, compared with RPNC, improves the detection of SGA and composite neonatal morbidity.

Sonographic fetal weight estimation in normal and overweight/obese healthy term pregnant women by gestation-adjusted projection (GAP) method

PURPOSE

The objective of this study is to assess the ultrasound accuracy in fetal weight estimation related to the time distance between the actual weight recorded at delivery and the period of sonography among normal and overweight/obese pregnant women within 3 weeks prior birth at term.

METHODS

Four-hundred and ninety patients with healthy pregnancy were studied in a cohort study. The absolute percent error in estimation was achieved by gestation-adjusted projection method from Hadlock model for weight calculation as measure of accuracy. The mean percentage error variation over the weeks was correlated to maternal body mass index (BMI, Kg/m(2)) at ultrasound. The relationship between BMI and ultrasound performance was assessed by linear regression.

RESULTS

The overall proportion of supposed sonographic estimated fetal weight at birth within ±10 % of the birth weight significantly declines over the weeks (P = .016). The trend toward a progressive deterioration in ultrasound accuracy is not statistically significant for normal weight women (P = .272) but it is for over-weight/obese (P = .044). On univariate analysis, the absolute percent error and absolute error are positively related to BMI.

CONCLUSIONS

Accuracy is related to the week at ultrasound scan with a gradual deterioration over the time and it worsens with increasing distance in days between the date of ultrasounds and delivery. The deterioration is greater for BMI ≥ 25.

Mode of delivery and outcomes by birth weight among spontaneous and induced singleton cephalic nulliparous labors

OBJECTIVE

To assess the effect of birth weight on mode of delivery among nulliparous women in a setting with no policy of elective induction for suspected macrosomia.

METHODS

In an observational study, data were assessed from nulliparous women with a single cephalic pregnancy of at least 37 weeks in spontaneous (Robson group 1) and induced (Robson group 2a) labor attending a hospital in Dublin, Ireland, between January 1, 2008, and December 31, 2009. The primary outcome measure was mode of delivery.

RESULTS

A total of 7528 nulliparous labors were included (4989 in group 1 and 2539 in group 2a). The cesarean section rate was 15.1% overall (n=1139), with 411 (8.2%) in group 1, and 728 (28.7%) in group 2a. Cesarean delivery rates rose with increasing birth weight in group 1, from 119 (6.3%) of 1886 infants weighing 3000-3499 g and 160 (8.5%) of 1892 weighing 3500-3999 g, to 19 (26.8%) of 71 weighing 4500-4999 g. Rates of cesarean delivery were significantly higher in induced labor (group 2a) for each birth-weight category, ranging from 202 (25.9%) of 781 weighing 3000-3499 g and 243 (27.0%) of 899 weighing 3500-3999 g, to 38 (48.1%) of 79 weighing 4500-4999 g (P<0.01 for all).

CONCLUSION

In a setting with standardized management of labor, birth weight remains a significant determinant of mode of delivery.

The influence of maternal body mass index on fetal weight estimation in twin pregnancy

OBJECTIVE

Sonographic estimated fetal weight (EFW) is important in the management of high-risk pregnancies. The possibility that increased maternal body mass index (BMI) adversely affects EFW assessments in twin pregnancies is controversial. The aim of this study was to investigate the effect of maternal BMI on the accuracy of EFW assessments in twin gestations prospectively recruited for the ESPRiT (Evaluation of Sonographic Predictors of Restricted growth in Twins) study.

STUDY DESIGN

One thousand one twin pair pregnancies were recruited. After exclusion, BMI, birthweights, and ultrasound determination of EFW (within 2 weeks of delivery) were available for 943 twin pairs. The accuracy of EFW determination was defined as the difference between EFW and actual birthweight for either twin (absolute difference and percent difference). Cells with less than 5% of the population were combined for analysis resulting in the following 3 maternal categories: (1) normal/underweight, (2) overweight, and (3) obese/extremely obese.

RESULTS

Analysis of the 3 categories revealed mean absolute variation values of 184 g (8.0%) in the normal/underweight group (n = 531), 196 g (8.5%) in the overweight group (n = 278), and 206 g (8.6%) in the obese/extremely obese group (n = 134) (P = .028, which was nonsignificant after adjustment for multiple testing). Regression analysis showed no linear or log-linear relationship between BMI and the accuracy of EFW (P value for absolute difference = .11, P value for percentage difference = .27).

CONCLUSION

Contrary to a commonly held clinical impression, increasing maternal BMI has no significant impact on the accuracy of EFW in twin pregnancy.

Periviable births: epidemiology and obstetrical antecedents

Confusion in terminology and non-standardized definitions can arguably be classified as the most important characteristics that lead to disparate study findings. While such situations abound in all of perinatal epidemiology, the study of "periviable birth" is a classic case in point. The most common term used to describe periviable birth has been extremely low birthweight (ELBW), often defined as newborns with birthweight below 1000g; yet, we identified 11 other descriptors for periviable birth. Due to the multitude of definitions, the reported incidence of periviable births varies from 0.03% to 1.9% (a relative difference of 7025%). Antecedent risk factors for periviable birth, though geographically heterogeneous, include nulliparity and multiple gestations, each accounting for one-third and one-fourth of all periviable births, respectively. Spontaneous preterm labor precedes 34% of these deliveries and premature rupture of membranes in 25%. The pregnancy was complicated by hypertensive disease in 21% and bleeding and chorioamnionitis in 18% each. Over 50% of these births are cesarean deliveries. Six clinical interventions before delivery that may improve outcomes include transfer of patient to a tertiary center, administration of antenatal corticosteroids, tocolytics, or antibiotics after premature rupture of membranes, assessment of fetal well-being with electronic fetal heart rate monitoring, and willingness to perform a cesarean delivery after the limit of viability is reached. While there is an accessible predictive model for mortality and long-term morbidities for newborns delivered at 22-25 weeks with weights of 400-1000g, it is hampered by the need to know the birthweight. In addition to reaching a consensus regarding what birthweight-gestational age thresholds determine a periviable birth, the acute need to optimize neonatal outcomes remains a paramount target worthy of future research, and efforts to advance obstetrical medicine are needed to minimize the likelihood of its occurrence.

Neonatal brachial plexus palsy with vaginal birth after cesarean delivery: a case-control study

OBJECTIVE

The objective was to determine the rate of neonatal brachial plexus palsy (NBPP) among women with vaginal birth after cesarean delivery (VBAC) and to compare the peripartum characteristics with control subjects.

STUDY DESIGN

The Maternal-Fetal Medicine Unit cesarean registry data were used to identify nonanomalous singleton pregnancies with VBAC and NBPP at gestational age of ≥37 weeks (term) and 4 control subjects (matched for gestational age and diabetes mellitus status but without brachial injury). Odds ratio (OR) and 95% confidence intervals (CIs) were calculated.

RESULTS

Among 11,313 VBACs at term, there were 23 women with NBPP (rate of 2.0/1000 women). Newborn infants with NBPP, compared with control infants, were significantly more likely to weigh ≥4000 g (48% vs 10%, respectively; OR, 8.45; 95% CI, 2.58-28.44) and to require admission to the neonatal intensive care unit (30% vs 13%; OR, 12.98; 95% CI, 2.61-72.18).

CONCLUSION

Women who desire VBAC should be informed about the low rate of NBPP and, if eligible, encouraged to have a trial of labor after cesarean delivery.

Fetal growth: a review of terms, concepts and issues relevant to obstetrics

The perinatal literature includes several potentially confusing and controversial terms and concepts related to fetal size and growth. This article discusses fetal growth from an obstetric perspective and addresses various issues including the physiologic mechanisms that determine fetal growth trajectories, known risk factors for abnormal fetal growth, diagnostic and prognostic issues related to restricted and excessive growth and temporal trends in fetal growth. Also addressed are distinctions between fetal growth 'standards' and fetal growth 'references', and between fetal growth charts based on estimated fetal weight vs those based on birth weight. Other concepts discussed include the incidence of fetal growth restriction in pregnancy (does the frequency of fetal growth restriction increase or decrease with increasing gestation?), the obstetric implications of studies showing associations between fetal growth and adult chronic illnesses (such as coronary heart disease) and the need for customizing fetal growth standards.

Accuracy of sonographic fetal weight estimation within 14 days of delivery in a Jordanian population using Hadlock formula 1

OBJECTIVES

To assess the accuracy of sonographic fetal weight estimation within 14 days of delivery in a Jordanian population using Hadlock formula 1 in the third trimester.

MATERIALS AND METHODS

Estimated fetal weights and actual fetal weights data were collected from the medical records of pregnant women who had undergone sonographic fetal weight estimation within 14 days of delivery over the period of March 2008 to June 2010. The analysis included 409 Jordanian women; 6 of them had twins, so the study involved estimation of 415 fetal weights, and these were compared to the actual recorded neonatal weights. Using Hadlock formula 1, we compared the estimations with the infants' actual birth weights. The data were analyzed in 2 groups: within 7 days and 8-14 days.

RESULTS

The mean estimated fetal weight was 3,133 ± 475 g (range 1,343-4,420 g). The mean actual birth weight was 3,179 ± 450 g (range 1,300-4,450 g). The mean absolute percentage of error of ultrasound fetal weight estimation for all infants was 6.5%; however, it was 6.1 and 8.2% if the fetus was delivered within 7 days or 8-14 days of sonography, respectively. Overall, 78.8% of fetal weight estimations were within 10% of actual birth weight; however it was 81.3 and 69.9% if the fetus was delivered within 7 days or from 8-14 days of sonography, respectively.

CONCLUSION

The use of Hadlock formula 1 for sonographic fetal weight estimations in Jordanian women showed acceptable results relative to the actual neonatal weight at birth. However, fetal weight estimation was more reliable when performed within 7 days of delivery.

Discordant twins: diagnosis, evaluation and management

Approximately 16% of twin gestations have discordance of at least 20%. We identified 14 risk factors for divergent growth that can be categorized as maternal, fetal, or placental. Determination of chorionicity and serial ultrasound evaluation with a high index of suspicion for divergent growth is required for the diagnosis and stratification of risk. The highest reported likelihood ratio for detection of discordance was 5.9 during the first trimester examination and 6.0 for the second trimester. Although our ability to identify discordant twins is limited, once suspected and at viable gestational age, these pregnancies should have antepartum testing. Discordant growth alone is not an indication for preterm birth. Although there are multiple publications on the increased morbidity and mortality rates with discordant growth, there is a paucity of reports on how to manage them optimally and deliver them in a timely manner.

Is the use of symphysis-fundal height measurement and ultrasound examination effective in detecting small or large fetuses?

We investigated the accuracy of using symphysis pubis-fundal height measurement and ultrasonically derived estimation of fetal weight for identifying small-for-gestational-age (SGA) and large-for-gestational-age (LGA) fetuses. A retrospective cohort study was performed using computerised records of all non-diabetic women referred for an ultrasound growth scan (US) with clinically suspected SGA or LGA singleton fetuses from 35 weeks' gestation between October 2008 and March 2009 (n = 185). Birth weight data were also collected for all births over the study period (n = 3200). One-third (34%) of ultrasound estimated fetal weights were inaccurate by >10%. However, an inaccurate ultrasound estimation did not significantly increase the likelihood of spontaneous or induced onset of labour or delivery by caesarean section. Most (79%) growth scans were performed on well-grown fetuses. The majority (80%) of SGA and LGA babies in our cohort were not identified by clinicians during routine antenatal care. From 3,200 live births, there were a total of 59 infants weighing <2,500 g or >5,000 g. Of these, only 12 had been referred for an ultrasound growth scan, indicating that abdominal palpation and fundal height measurement has a 20% sensitivity in detecting SGA or LGA fetuses. Of the 12, four were detected using ultrasound, indicating a 33% detection rate. Although ultrasound has a slightly higher sensitivity, neither clinical examination using fundal height measurements nor 3rd trimester ultrasound examinations are effective at detecting SGA or LGA fetuses.

Oligohydramnios, small for gestational age and pregnancy outcomes: an analysis using precise measures

BACKGROUND/AIM

Marginal or decreased amniotic fluid volume by ultrasound estimate and fetal growth restriction have been shown to be significantly associated with perinatal mortality. The association of fetal growth restriction and precisely measured amniotic fluid volume is unknown. The purpose of this study was to determine if adverse pregnancy outcomes are more likely in pregnancies complicated by small-for-gestational-age (SGA) neonates and dye-determined oligohydramnios.

METHODS

Admissions to neonatal intensive care unit (NICU) and other pregnancy outcomes were analyzed in parturients with known amniotic fluid volume, calculated by the dye-dilution technique. The pregnancy outcomes of those with oligohydramnios and SGA were compared with pregnancies complicated by just one of these two conditions and pregnancies with normal fluid and birth weight.

RESULTS

Of 202 patients, oligohydramnios was present in 26% (53), SGA in 15% (30) and both conditions in (5%) (11). Logistic regression, controlling for gestational age, demonstrated that the combination of oligohydramnios and SGA, compared to normal growth and fluid strongly predicted NICU admission (OR 11.1; 95% CI 2.1-59.2) but not other complications. (OR 4.8; 95% CI 0.3-62.9).

CONCLUSIONS

SGA with oligohydramnios significantly increases the likelihood of a NICU admission, but not other morbidity.

New insights on vaginal birth after cesarean: can it be predicted?

OBJECTIVE

To evaluate existing vaginal birth after cesarean (VBAC) screening tools and to identify additional factors that may predict VBAC or failed trial of labor.

DATA SOURCES

Relevant studies were identified through MEDLINE, Database of Abstracts of Reviews of Effectiveness, and the Cochrane databases (1980-September 2009), and from recent systematic reviews, reference lists, reviews, editorials, web sites, and experts.

METHODS OF STUDY SELECTION

Inclusion criteria limited studies to those of humans, written in English, studies conducted in the United States and developed countries, and those rated good or fair quality by the U.S. Preventive Services Task Force criteria. Studies of individual predictors were combined using a random effects model when the estimated odds ratios were comparable across included studies.

TABULATION, INTEGRATION, AND RESULTS

We identified 3,134 citations and reviewed 963 papers, of which 203 met inclusion criteria and were quality-rated. Twenty-eight provided evidence on predictors of VBAC and 16 presented information on scored models for predicting VBAC (or failed trial of labor). Six of the 11 scored models for predicting VBAC (or failed trial of labor) were validated by separated dataset, cross-validation, or both. Whereas accuracy remained high across all models for predicting VBAC, with predictive values ranging from 88% to 95%, accuracy for predicting failed trial of labor was low, ranging from 33% to 58%. Individual predictors including Hispanic ethnicity, African-American race, advanced maternal age, no previous vaginal birth history, birth weight heavier than 4 kg, and use of either augmentation or induction were all associated with reduced likelihood of VBAC.

CONCLUSION

Current scored models provide reasonable predictability for VBAC, but none provides consistent ability to identify women at risk for failed trial of labor. A scoring model is needed that incorporates known antepartum factors and can be adjusted for current obstetric factors and labor patterns if induction or augmentation is needed. This would allow women and clinicians to better determine individuals most likely to require repeat cesarean delivery.

Limitations of ultrasound in diagnosing intrauterine growth restriction in severe preeclampsia

OBJECTIVE

The objective of this study was to determine test characteristics of ultrasound in detecting intrauterine growth restriction (IUGR) in severe preeclampsia (S-PEC).

STUDY DESIGN

We performed a prospective study (2005-2007) to evaluate risk factors for PEC. Women with severe PEC and an ultrasound <or=3 weeks of delivery were enrolled. Chi square analysis determined associations between diagnosis of IUGR and small for gestational age (SGA) birth weight. Multivariable logistic regression was used to control for confounders. Fetal growth rate and test characteristics of ultrasound were calculated.

RESULTS

Ninety-three patients were enrolled. There was a significant association between IUGR and SGA, but no association between maternal demographic factors and IUGR. Test characteristics of ultrasound to diagnose IUGR in severe PEC were: sensitivity 56.7%, specificity 93.7%, PPV 81.0%, NPV 81.9%. The positive likelihood ratio (+LR) for ultrasound to detect IUGR in severe PEC was 8.9.

CONCLUSION

Current ultrasound practice has moderately good positive and negative predictive values and a high specificity for the diagnosis of IUGR in women with severe PEC. However, the poor sensitivity and low + LR indicate that additional modalities are needed to improve the usefulness of ultrasound in detecting IUGR in severe PEC.

A scoring system for detection of macrosomia and prediction of shoulder dystocia: A disappointment

OBJECTIVE

To develop a scoring system for the detection of a macrosomic fetus (birth weight (BW) >or= 4000 g) and predict shoulder dystocia among large for gestational age fetuses.

STUDY DESIGN

We retrospectively identified all singletons with accurate gestational age (GA) that were large for GA (abdominal circumference (AC) or estimated fetal weight (EFW) >or= 90% for GA) at >or=37 weeks with delivery within three weeks. The scoring system was: 2 points for biparietal diameter, head circumference, AC, or femur length >or=90% for GA, or if the amniotic fluid index (AFI) was >or=24 cm; for biometric parameters <90% or with AFI <24 cm, 0 points. The predictive values for detection of shoulder dystocia were calculated.

RESULTS

Of the 225 cohorts that met the inclusion criteria the rate of macrosomia was 39% and among vaginal deliveries (n = 120) shoulder dystocia occurred in 12% (15/120; 95% confidence interval (CI) 7-20%). The sensitivity of EFW >or=4500 g to identify a newborn with shoulder dystocia was 0% (95% CI 0-21%), positive predictive values 0% (95% CI 0-46%), and likelihood ratio of 0. For a macrosomia score >6, the corresponding values were 20% (4-48%), 25% (5-57%) and 2.3.

CONCLUSION

Though the scoring system can identify macrosomia, it offers no advantage over EFW. The scoring system and EFW are poor predictors of shoulder dystocia.