Diabetic macrosomia: accuracy of third trimester ultrasound

Sonar biparietal diameter, head circumference, and abdominal circumference percentile values obtained late in the third trimester were compared with birth weight percentile (relative to dates) in 147 diabetic mothers and 40 control fetuses of nondiabetics. Estimates of fetal weight by the method of Shepard et al were also calculated from these sonar data and compared with birth weight percentile. Abdominal circumference values greater than the 90th percentile correctly predicted macrosomia (defined as birth weight greater than 90th percentile) in 78% of cases. Biparietal diameter and head circumference percentiles were significantly less predictive of macrosomia. When analyzed in a similar manner, estimated fetal weights greater than the 90th percentile correctly predicted macrosomia at birth in 74% of cases. However, when both the abdominal circumference and the estimated fetal weight exceeded the 90th percentile, macrosomia was correctly diagnosed in 88.8% of pregnant women with diabetes mellitus.     

A comparison of single versus multiple growth ultrasonographic examinations in predicting birth weight

OBJECTIVE: Our purpose was to determine whether two or more ultrasonographic fetal growth assessments provide a superior estimate of birth weight than does a single examination. STUDY DESIGN: Five hundred and eighty five ultrasonographic procedures were performed in 263 patients, divided into single (n = 249) and multiple (n = 247) examination groups. Ultrasonographically estimated fetal weight percentiles and abdominal circumference percentiles were compared with gestationally corrected birth weight percentiles. After the gestational age range with the fewest errors in birth weight percentile prediction (32 to 36 weeks) was determined, patients with a single examination in this range were assigned to the single examination group. In the group with multiple examinations averaged ultrasonographic percentiles were used to predict birth weight percentile. Mean absolute and percentage errors were compared for predictive accuracy by means of analysis of variance and Student t test. RESULTS: There was a linear correlation between the estimated fetal weight and abdominal circumference percentiles and the birth weight percentile, (r = 0.72, p < 0.0001). The accuracy of birth weight percentile predictions was similar whether one or multiple examinations were performed in the third trimester. Both the abdominal circumference percentile and estimated fetal weight percentile underpredicted birth weight, although the abdominal circumference percentile errors (1% to 2%) were statistically smaller than those derived from estimated fetal weights percentile (9% to 11%, p < 0.0001). Both abdominal circumference percentile and estimated fetal weights percentile consistently overidentified fetuses <10th percentile (small for gestational age) and underidentified fetuses >90th percentile (large for gestational age). However, multiple abdominal circumference percentile measurements resulted in improved predictions for small for gestational age (sensitivity 100%, specificity 88%) and large for gestational age (sensitivity 84%, specificity 100%). CONCLUSIONS: With either the single or multiple examination approach birth weight percentile estimates were within 10% of the actual birth weight percentile approximately 50% of the time. Multiple ultrasonographic examinations provided little improvement in prediction of birth weight compared with a single observation. Multiple measurements of the abdominal circumference percentile may provide improved accuracy in identifying large for gestational age and small for gestational age fetuses. (AM J Obstet Gynecol 1994;170:1600-6.)     

The risks of spontaneous preterm delivery and perinatal mortality in relation to size at birth according to fetal versus neonatal growth standards

OBJECTIVE: The aim of this study was to test the null hypothesis that size at birth relative to fetal or neonatal growth standards is not a significant variable related to the risk of spontaneous preterm delivery. STUDY DESIGN: This was a hospital-based cohort study of consecutive births at a tertiary care perinatal center from January 1, 1985, to December 31, 1996. A total of 37,377 pregnancies met the following inclusion criteria: (1) singleton gestation, (2) 25 to 40 weeks' gestation, and (3) no anomalies. Neonates were divided into 5 birth weight categories according to either fetal (uncorrected for sex) or neonatal (corrected for sex) growth standards, as follows: (1) intrauterine growth restriction, birth weight <3rd percentile; (2) borderline intrauterine growth restriction, birth weight > or = 3rd percentile and <10th percentile; (3) appropriate for gestational age, birth weight from 10th percentile through 90th percentile; (4) borderline large for gestational age, birth weight >90th percentile but < or = 97th percentile, and (5) large for gestational age, birth weight >97th percentile. Logistic regression analysis was used to estimate the independent effect of birth weight category on the risk of preterm delivery after spontaneous onset of labor, with the appropriate-for-gestational-age group serving as a reference. RESULTS: When fetal growth standards were applied, there was a significant increase in the risk of spontaneous preterm delivery when birth weight was outside the appropriate-for-gestational-age range (odds ratios of 2.5, 1.4, 1.2, and 1.9 for intrauterine growth restriction, borderline intrauterine growth restriction, borderline large-for-gestational age, and large-for-gestational-age groups, respectively). In contrast, when neonatal growth standards were applied, the risks of spontaneous preterm delivery in intrauterine growth restriction, borderline intrauterine growth restriction, and large-for-gestational-age groups were significantly lower (odds ratios of 0.5, 0.7, and 0.7 for intrauterine growth restriction, borderline intrauterine growth restriction, and large-for-gestational-age groups, respectively) because of an underestimation in the number of fetuses with abnormal size at birth delivered prematurely. With both fetal and neonatal growth standards there was a 5-to 6-fold greater risk of perinatal death for both preterm and term fetuses with intrauterine growth restriction. CONCLUSION: Fetal growth standards are more appropriate in predicting the impact of birth weight category on the risk of spontaneous preterm delivery than are neonatal growth standards. When fetal standards are applied, the risks of preterm birth in both extreme abnormal birth weight categories (intrauterine growth restriction and large for gestational age) are 2- to 3-fold greater than the risk among appropriate-for-gestational-age infants.     

The influence of fetal sex on the antenatal diagnosis of small for gestational age

Objective: We evaluated the influence of fetal sex on the antenatal diagnosis and detection of small for gestational age (SGA).

Methods: The cohort consisted of unselected singleton pregnancies, undergoing routine biometry and cerebroplacental ratio (CPR) assessment at 36 weeks. Locally fitted equations for centiles and Z scores were used. “Ultrasound SGA” was defined as estimated fetal weight (EFW)?Results: Among 4112 pregnancies, there were 235 female “ultrasound SGA” fetuses and 177 male; (odds ratios (OR) 1.502 (1.223???1.845)); the detection rate of SGA at birth was 50.6% and 40.9%, respectively (OR 1.479 (0.980???2.228)). In “ultrasound SGA” girls the abdominal circumference growth velocity (ACGV) between 20 and 36 weeks was less frequently in the lowest decile (OR 0.490 (0.320???0.750)), with no differences in CPR.

Conclusions: Females are more commonly diagnosed as SGA; those diagnosed may be at less risk than males.     

A prediction score to assess the risk of delivering a large for gestational age infant among obese women

Objective: To create a prediction score incorporating both maternal clinical characteristics and sonographic measurements in an effort to more accurately determine the risk of a large for gestational age (LGA) infant in the obese gravida.

Methods: We performed a retrospective cohort study of obese women with singleton pregnancies who had a fetal ultrasound performed between 32 and 36 weeks from 1/2008 to 12/2011. LGA was defined as birth weight (BW) ≥90%. Clinical characteristics associated with fetal overgrowth were included in a multivariable logistic model and stepwise backwards regression was performed to identify which risk factors generated the most parsimonious predictive model. Adjusted odds ratios of covariates in the final model were used to estimate weights for each risk factor that were summed to generate a predictive score.

Results: Six-hundred and sixty-nine obese women were included. The incidence of LGA infants was 11.8%. Ultrasound estimation of fetal weight alone accurately predicted LGA in 17.7 % of cases (AUC?=?0.58). The most parsimonious model to accurately predict LGA at birth included 3rd trimester ultrasound EFW >90th percentile, interval from scan to delivery, and maternal history of diabetes mellitus (DM) (AUC?=?0.74). A positive prediction score test result was associated with 92% specificity and 89% negative predictive value.

Conclusions: A clinical prediction rule was developed and internally validated to predict the risk of an LGA infant among obese women. The ability to calculate a prediction score at the time of delivery is appealing to the clinician in order to accurately counsel women regarding the risks surrounding the delivery.     

Influence of difficulty of instrumentation with vacuum on the rate of levator ani muscle avulsion identified by 3–4 d transperineal ultrasound

Objectives: Evaluation of the influence of difficulty of instrumentation with vacuum on the rate of levator ani muscle (LAM) avulsions.

Materials and methods: Prospective observational study with 86 nulliparous women with at term gestation who required instrumentation with vacuum to complete fetal extraction. After every delivery, each explorer reported the number of vacuum tractions needed to complete fetal extraction, as well as the subjective complexity of the instrumentation. LAM avulsion rate was assessed by 3D–4D transperineal ultrasound evaluation 6 months after delivery.

Results: Seventy nine cases were evaluated and classified as either “easy” delivery (below three vacuum tractions; n?=?49) or “difficult” delivery (three or more vacuum tractions; n?=?30). No differences in obstetric characteristics were observed between study groups, with the following exceptions: fetal head circumference (34.8?±?2.7 versus 35.2?±?1.1; p?=?.013) and fetal weight at birth (3260?±?421 versus 3500?±?421; p?=?.016). No statistically significant differences between study groups were observed in LAM avulsion rate (36.7 versus 30%) and levator hiatus area (cm²) at rest (18.44?±?3.95 versus 17.75?±?3.90).

Conclusions: The number of vacuum tractions needed to complete fetal extraction is not associated to a higher LAM avulsion rate nor with differences in levator hiatus area.     

Predicting late-onset growth abnormalities using growth velocity between trimesters

Objectives.?To determine whether growth velocity parameters derived from routine prenatal ultrasound measurements at first, second and third trimester can identify normal growth at term as well as late-onset growth abnormalities.

Material and methods.?Longitudinal study of fetal growth in normal singleton pregnancies with three normal ultrasound examinations and delivered at term. Fetuses were classified into 3 groups (?<?10th percentile, 10–90th percentile, >?90th percentile) based on birth weight. Multiple regression on birth weight classification was used to build up a prediction equation of fetal growth potential (FGP) based on fetal biometry and fetal growth velocity parameters between ultrasound examinations. Best cut-off value for FGP predicting growth restriction and macrosomia were defined.

Results.?356 pregnancies were included. Fetal biometry growth velocities between examinations were calculated for all measurements. Using best cut-off values, the estimated sensitivity, specificity and odds ratio were: 60% [44;74], 91%[89;92] and 14.55 [6.30;33.98] and 53% [36;69], 89%[88;91] and 10 [4.27;23.49] for the prediction of growth restriction and macrosomia, respectively.

Discussion.?Fetal growth potential can be derived and calculated from standard ultrasound measurements. It can improve identification of these fetuses at risk for late-onset growth abnormalities and their related morbidity.     

Histologic chorioamnionitis is associated with fetal growth restriction in term and preterm infants

OBJECTIVE: Our aim was to evaluate associations between chorioamnionitis and fetal growth restriction in infants enrolled in the Collaborative Perinatal Project. STUDY DESIGN: A total of 2579 nonanomalous, singleton infants delivered at 28 to 44 weeks' gestation with chorioamnionitis were matched 1:3 for ethnicity, gestational age, parity, and maternal cigarette use (all of which were correlated with both chorioamnionitis and markers of fetal growth restriction) with 7732 control infants. Moderate or marked leukocytic infiltrates of the placenta defined chorioamnionitis. Birth weight, length, head circumference, weight/length ratio, ponderal index, and birth weight/head circumference ratio in the lowest 5th percentile were markers of fetal growth restriction. Placental weight and the birth weight/placental weight ratio were also evaluated. RESULTS: Compared with data on matched control infants, histologic chorioamnionitis was associated with all markers of fetal growth restriction and with low birth weight/placental weight ratios (odds ratios, 1.3-1.7). The strongest associations were found at 28 to 32 weeks' gestation (odds ratios, 2.2-11). Attributable risks for several markers of fetal growth restriction exceeded 50% in infants born at <33 weeks' gestation. CONCLUSION: Histologic chorioamnionitis is associated with multiple markers of fetal growth restriction, with stronger associations noted in prematurity.     

Improving customized fetal biometry by longitudinal modelling

Objective: To develop customized biometric charts to better define abnormal fetal growth.

Methods: A total of 1056 singleton fetuses from the Raine Study underwent serial ultrasound biometry (abdominal circumference [AC], head circumference, and femur length) at 18, 24, 28, 34, and 38 weeks’ gestation. Customized biometry trajectories were developed adjusting for epidemiological influences upon fetal biometry using covariates available at 18 weeks gestation. Prediction accuracy (areas under the receiver operating characteristic curve [AUC] and 95% confidence interval [95%CI]) was evaluated by repeated random sub-sampling cross-validation methodology.

Results: The model for derived estimated fetal weight (EFW) performed well for EFW less than 10th predicted percentile (AUC?=?0.695, 95%CI, 0.692–0.699) and EFW greater than 90th predicted percentile (AUC?=?0.705, 95%CI, 0.702–0.708). Fetal AC was also well predicted for growth restriction (AUC?=?0.789, 95%CI, 0.784–0.794) and macrosomia (AUC?=?0.796, 95%CI, 0.793–0.799). Population-derived, sex-specific charts misclassified 7.9% of small fetuses and 10.7% of large fetuses as normal. Conversely, 9.2% of those classified as abnormally grown by population-derived charts were considered normal by customized charts, potentially leading to complications of unnecessary intervention.

Conclusions: Customized fetal biometric charts may offer improved ability for clinicians to detect deviations from optimal fetal growth and influence pregnancy management.     

The growth-restricted fetus: risk of mortality by each additional week of expectant management

Objective: To compare fetal/infant mortality risk associated with each additional week of expectant management with the infant mortality risk of immediate delivery in growth-restricted pregnancies.

Methods: A retrospective cohort study was conducted of singleton, nonanomalous pregnancies from the 2005–2008 California Birth Registry comparing pregnancies affected and unaffected by growth restriction, defined using birth weights as a proxy for fetal growth restriction (FGR). Birth weights were subdivided as greater than the 90th percentile, between the 10th percentile and 90th percentile, and less than the 10th percentile. Cases greater than the 90th percentile were excluded from analysis. Cases less than the 10th percentile were considered to have FGR and were further subcategorized into <10th percentile, <5th percentile, and <3rd percentile. We compared the risk of infant death at each gestational age week against a composite risk representing the mortality risk of one additional week of expectant management.

Results: We identified 1,641,000 births, of which 110,748 (6.7%) were less than 10th percentile. The risk of stillbirth increased with gestational age with the risk of stillbirth at each week of gestation inversely proportional to growth percentile. The risks of fetal and infant mortality with expectant management outweighed the risk of infant death for all FGR categories analyzed beginning at 38 weeks. However, the absolute risks differed by growth percentiles, with the highest risks of infant death and stillbirth in the <3rd percentile cohort. At 39 weeks, absolute risks were low, although the number needed to deliver to prevent 1 death ranged from 413 for <3rd percentile to 2667 in unaffected pregnancies.

Conclusion: At 38 weeks, the mortality risk of expectant management for one additional week exceeds the risk of delivery across all growth-restricted cohorts, despite variation in absolute risk by degree of growth restriction.     

Placental location and newborn weight

ObjectivePrevious studies suggest that placental location may affect fetal growth and the risks of preterm birth and preeclampsia. We studied the association between placental location and newborn weight.MethodsWe conducted a retrospective cohort study of 796 consecutive singleton births in women who delivered at ≥ 37 weeks’ gestation between July and October 2009. We evaluated placental location at the time of the second trimester prenatal ultrasound at 16 to 24 weeks’ gestation. Placental location was classified as lateral or central/fundal. We assessed the difference in newborn weight according to placental location and the incidence of small for gestational age birth weight < 10th percentile and pregnancy-induced hypertension. Using logistic regression analysis, odds ratios were adjusted for maternal age, world region of birth, gravidity, parity, maternal weight, history of hypertension or diabetes, current smoking or illicit drug use, and infant sex.ResultsAmong women with lateral versus central/fundal placentas, the respective mean (SD) birth weights were 3298 (550) g and 3352 (579) g (mean difference 54 g, 95% CI 53 to 161; P = 0.32). Relative to central/fundal location, laterally located placentas had an adjusted OR of 0.81 (95% CI 0.42 to 1.54) for SGA and 0.62 (95% CI 0.18 to 2.10) for preeclampsia/gestational hypertension.ConclusionPlacental location was not associated with differences in newborn weight or other perinatal outcomes.     

Risk factors for failed vacuum extraction and associated complications in term newborn infants: a population-based cohort study

Objective: The aims of the present study were to investigate risk factors for failed vacuum extraction (VE), and to compare neonatal complications among infants delivered by failed VE with those delivered by successful VE.

Methods: Population-based study including all women (and their newborn infants) with singleton pregnancy who gave birth at term by failed VE (n?=?4747) or successful VE (n?=?83?671) in Sweden between 1999 and 2010. Failed VE was defined as VE followed by an emergency cesarean section (ECS), forceps, or both forceps and ECS. We used logistic regression to examine the association between failed VE in relation to intracranial hemorrhage, subgaleal hemorrhage, Apgar scores <7 at 5?min, and neonatal convulsions.

Results: Risk factors for failed VE included occipito posterior position, mid-pelvic fetal station, high birth weight, short maternal stature, epidural analgesia, and induction of labor. Compared with infants born after a successful VE, those delivered by failed VE had a higher risk of subgaleal hemorrhage OR 7.3 CI (5.5–9.7), convulsions OR 1.9 CI (1.4–2.7), and low Apgar OR 2.6 CI (2.3–3.0), but not of ICH.

Conclusion: Failed VE is associated with neonatal complications. Fetal head position and station should be carefully assessed prior to the extraction.     

Birth weight curves tailored to maternal world region

BackgroundNewborns of certain immigrant mothers are smaller at birth than those of domestically born mothers. Contemporary, population-derived percentile curves for these newborns are lacking, as are estimates of their risk of being misclassified as too small or too large using conventional rather than tailored birth weight curves.MethodsWe completed a population-based study of 766 688 singleton live births in Ontario from 2002 to 2007. Smoothed birth weight percentile curves were generated for males and females, categorized by maternal world region of birth: Canada (63.5%), Europe/Western nations (7.6%), Africa/Caribbean (4.9%), Middle East/North Africa (3.4%), Latin America (3.4%), East Asia/Pacific (8.1%), and South Asia (9.2%). We determined the likelihood of misclassifying an infant as small for gestational age (≤ 10th percentile for weight) or as large for gestational age (≥ 90th percentile for weight) on a Canadian-born maternal curve versus one specific to maternal world region of origin.ResultsSignificantly lower birth weights were seen at gestationspecific 10th, 50th, and 90th percentiles among term infants born to mothers from each world region, with the exception of Europe/Western nations, compared with those for infants of Canadian-born mothers. For example, for South Asian babies born at 40 weeks’ gestation, the absolute difference at the 10th percentile was 198 g (95% CI 183 to 212) for males and 170 g (95% CI 161 to 179) for females. Controlling for maternal age and parity, South Asian males had an odds ratio of 2.60 (95% CI 2.53 to 2.68) of being misclassified as small for gestational age, equivalent to approximately 116 in 1000 newborns; for South Asian females the OR was 2.41 (95% CI 2.34 to 2.48), equivalent to approximately 106 per 1000 newborns. Large for gestational age would be missed in approximately 61 per 1000 male and 57 per 1000 female South Asian newborns if conventional rather than ethnicity-specific birth weight curves were used.ConclusionsBirth weight curves need to be modified for newborns of immigrant mothers originating from non-European/Western nations.     

Use of Second-Trimester Fetal Growth Curves in Predicting Intrauterine Growth Retardation in Cases of Unexplained Maternal Serum α-Fetoprotein Elevations

We sought to assess the ability of second-trimester fetal growth curves in predicting intrauterine growth retardation at birth in cases of unexplained elevated maternal serum a-fetoprotein (MSAFP). Singleton pregnancies with a single MSAFP ≥2.0 multiples of the median were eligible if a targeted ultrasound prior to 24 weeks agreed with dates and revealed no fetoplacental anomaly. Using Hadlock's formulas (biparietal diameter, femur length, abdominal circumference), the initial second trimester fetal weight estimation was stratified into percentiles using institutionally established second trimester fetal growth curves. In 303 patients, 35 nonanomalous growth regarded infants were delivered. The sensitivity (17-77%), specificity (61-100%), positive (21-100%), and negative (87-95%) predictive values were determined for estimated fetal weight cutoffs of < 10th and <50th percentile and MSAFP elevations ≥2.0 and >2.5 MoM. In pregnancies with an unexplained elevated MSAFP, second trimester growth curves can assist the clinician in discriminating between pregnancies at high risk of subsequent intrauterine growth retardation (positive predictive value of an estimated fetal weight of < 10th percentile, 60-100%) and in need of serial ultrasounds for growth, and those at low risk of intrauterine growth retardation at birth (negative predictive value of an estimated fetal weight of <50th percentile, 93-95%) not requiring such intervention.     

Weight gain during pregnancy in adolescence: predictive ability of early weight gain

Pregnancy weight gains were examined at 4-week intervals from 12-36 weeks' gestation and total gain assessed at delivery in a cohort of 2008 pregnant women aged 18 or less at entry to prenatal care. As early as 12 weeks' gestation, there was a significant association between the amount of weight gained and infant birth weight measured at the time of delivery. At 16 weeks' gestation, gains below the 25th percentile were associated with an increased risk of low birth weight (LBW) (adjusted odds ratio 1.56; 95% confidence interval 1.01-2.43), and by 20 weeks' gestation, the risk of LBW was doubled (adjusted odds ratio 2.00; 95% confidence interval 1.34-2.99). Also at 16 weeks, there was a doubling in the risk of excessive fetal size or macrosomia (adjusted odds ratio 2.31; 95% confidence interval 1.31-4.10) associated with maternal weight gain above the 75th percentile. These results suggest that an increased risk of certain poor pregnancy outcomes is detectable late in the first or early in the second trimester. Consequently, weight gain monitoring may be important early in pregnancy.     

Evaluation of the adequacy of Hadlock’s reference chart for identification of fetuses with growth restriction

Objective: This study aimed to verify whether Hadlock’s reference values for fetal weight identify fetuses below the 10th percentile in our population correctly.

Methods: The fitness of the Hadlock reference range to our study population was tested by assessment of Z scores. We evaluated differences between the reference weight ranges proposed in our study and those recommended by Hadlock.

Results: Z scores for Hadlock reference values were non-normally distributed. The difference between the 50th percentile fetal weight proposed by our study model and that proposed by Hadlock was ≤1% at GAs ≥22 weeks and 2–3% at 19–21 weeks. For the 90th percentile level, the maximum difference at GAs ≥17 weeks was 1.5%. For the 10th percentile level, the differences were 2–4% in the third trimester, reaching 8% in week 20 and 13% at a GA of 14 weeks.

Conclusions: The weight reference ranges of this study virtually overlap with the Hadlock ranges. We believe that only at lower gestational ages in the second trimester might some FGR diagnoses be missed in the population study with Hadlock’s reference.     

Differences in amniotic fluid patterns and fetal biometric parameters in third trimester pregnancies with and without diabetes

Objective.?The amniotic fluid index (AFI) has been increasingly used in the assessment of fetal well-being. We conducted the study to evaluate and compare the amniotic fluid index in third trimester normal and diabetic human pregnancy and to assess the correlation between the AFI and the fetal biometric parameters.

Methods.?Real-time ultrasound was performed to evaluate the AFI (four-quadrant technique), and to measure the biparietal diameter, head circumference, abdominal circumference, and femur length in 225 normal and 120 diabetic pregnant women from 27 to 42 weeks of gestation. Each patient was studied only once.

Results.?AFI in normal pregnancies was less than that in diabetic pregnancies throughout the gestational ages studied (27–42 weeks). In normal pregnancy, the mean AFI was 14.0 cm at 27 weeks and decreased to 11.4 cm at 42 weeks (r = 0.25, p = 0.0005), whereas in diabetic pregnancies, the values remained stable throughout the gestational ages studied. There exist significant differences in AFI, estimated fetal weight, estimated fetal weight %, abdominal circumference, abdominal circumference %, and head circumference to abdominal circumference ratio between the two groups. In both normal and diabetic pregnancies, there is a positive correlation between the AFI and the percentile of abdominal circumference (p < 0.0001), and between the AFI and the percentile of estimated fetal weight (p < 0.0001).

Conclusion.?This study provides gestational age-specific values of the AFI in normal and diabetic pregnancies. Diabetic pregnancy has greater AFI values than normal pregnancy between 27 and 42 weeks. The AFI correlates to the percentile of the estimated fetal weight and the abdominal circumference in both groups, suggesting that there may be a relationship between increased AFI and large for gestational age fetus independent of diabetes.     

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) ≥ 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) ≥ 90% for GA) at ≥37 weeks with delivery within three weeks. The scoring system was: 2 points for biparietal diameter, head circumference, AC, or femur length ≥90% for GA, or if the amniotic fluid index (AFI) was ≥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 ≥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.     

Defining fetal growth restriction: abdominal circumference as an alternative criterion

Purpose: The purpose of this study is to determine if using abdominal circumference percentile (AC) to define fetal growth restriction (FGR) improves ultrasound at ≥36 weeks as a screening test for small for gestational age (SGA).

Materials and methods: All non-anomalous singletons undergoing ultrasound at a single center at ≥36 weeks during 12/2008–5/2014 were included. FGR was defined as (estimated fetal weight) estimated fetal weight (EFW) and/or abdominal circumference (AC)?Results: There were 1594 ultrasounds. Median (IQR) ultrasound GA was 37.3 (36.6–38.0), days to delivery 10.6 (5.0–18.4), and delivery GA 39.29 (38.6–39.9). EFW <10 had the following characteristics: sensitivity 50.6%, FPR 2.0%, PPV 83.8%, and AUC 0.743. Using AC <10, these were 64.0, 2.9, 81.3, and 0.806, respectively. Using AC or EFW <10, these were 67.5, 3.3, 80.3, and 0.821, respectively; this criterion has the largest AUC (p?Conclusions: AC <10 is more sensitive and has a similar PPV compared with EFW <10 for SGA. Using AC <10 or EFW <10 has the best balance of sensitivity and specificity as a screening test and has a low FPR. AC may be a reasonable alternative criterion to EFW for FGR diagnosis.