Effectiveness of ultrasound determination of fetal abdominal circumference and fetal ponderal index in the diagnosis of asymmetrical growth retardation

Summary. A total of 310 unselected women attending an antenatal clinic was screened for growth retardation by ultrasound between 34 and 36 weeks gestation, by measuring the fetal abdominal circumference (AC) and femoral length (FL), from which the 'fetal ponderal index' (AC/FL) was calculated. Asymmetrical growth retardation in the newborn was assessed by Rohrer's ponderal index and the mid-arm/ occipito-frontal circumference (MAC/OFC) ratio within 72 h of birth, a neonatal ponderal index or MAC/OFC ratio below the 10th centile being considered abnormal. The sensitivities of an AC below the 25th centile in identifying a birthweight, neonatal ponderal index or MAC/ OFC ratio below the 10th centile were 86, 62 and 67% respectively, the specificities being 80, 78 and 76%. The sensitivities of a fetal ponderal index below the 25th centile in identifying a neonatal ponderal index or MAC/OFC ratio below the 10th centile were 52 and 47% respectively, the specificities being 77 and 77%. A possible reason for the poor performance of the fetal ponderal index is discussed.     

Relationship between customised birthweight centiles and neonatal anthropometric features of growth restriction

Objective To determine the relationship between customised birthweight centiles (adjusted for maternal and fetal physiological variables) and neonatal anthropometric features of intrauterine growth restriction (IUGR).
Design Observational study.
Population Two-hundred and seventy women with low risk pregnancies participating in a cohort study of serial ultrasound biometry.
Methods Customised birthweight centiles were calculated following adjustment for maternal weight, height and ethnic origin, gestational age at delivery, birth order, and sex of the infant. Three separate neonatal anthropometric measures were used to define IUGR: subscapular or triceps skinfold thickness  <10th  centile; ponderal index  <25th  centile; and mid-arm circumference to occipito-frontal circumference ratio (MAC/OFC) <−1 standard deviation (SD). Relationship of the centiles to these outcomes was evaluated using likelihood ratios (LR) and kappa statistic. These approaches allowed us to examine the strength of the association: an LR of 5–10 would be expected to generate moderate changes in the pre-test probability of IUGR, whereas a kappa value of 0.2–0.4 would reflect fair agreement between customised birthweight centiles and neonatal anthropometric measures.
Results Customised birthweight centile of 10 or less had the following LR values for the various anthropometric criteria for IUGR: 5.1 (95% CI 3–8.5) for low skinfold thickness; 4.3 (95% CI 2.5–7.1) for low ponderal index; and 3.9 (95% CI 2–6.6) for low MAC/OFC ratio. The kappa values were: 0.4 (95% CI 0.26–0.51) for low skinfold thickness; 0.33 (95% CI 0.21–0.46) for low ponderal index; and 0.13 (95% CI 0–0.26) for low MAC/OFC ratio.
Conclusion In a low risk population, customised birthweight centiles can only be moderately useful in the identification of neonates with low skinfold thickness and low ponderal index.     

Sonographic diagnosis of intrauterine growth retardation using the postnatal ponderal index and the crown-heel length as standards of diagnosis

One hundred twenty-one patients underwent an ultrasound examination within 48 hours of delivery to assess prospectively the reliability of the diagnosis of intrauterine growth retardation. Sonographic parameters examined included the abdominal circumference, sonographic estimate of fetal weight, the head to abdominal circumference ratio, and the femur length to abdominal circumference ratio. The best obstetric estimate of gestational age was used. The diagnosis of growth retardation was based on the postnatal ponderal index, and or the birthweight and crown-heel length percentiles. Seventeen infants were growth retarded. Fifteen infants had a birthweight less than the 10th percentile, but only nine (60%) were either asymmetrically growth retarded (by their ponderal index) or symmetrically growth retarded (by virtue of a birthweight and length less than the 10th percentile). All sonographic parameters were better able to predict a birthweight below the 10th percentile for gestational age than growth retardation. An abdominal circumference less than the 2.5 percentile for gestational age had the highest sensitivity for growth retardation (88.0%) of the parameters studied. Only the abdominal circumference centile identified all infants with either symmetric growth retardation or asymmetric growth retardation associated with a birthweight below the 10th percentile. A sonographic estimate of fetal weight below the 10th percentile had the highest positive predictive value for growth retardation--38%. In contrast to the overall poor positive predictive values, the negative predictive values for all parameters studied exceeded 90%. Combining the abdominal circumference percentile with one of the three remaining techniques did not significantly improve diagnostic accuracy.(ABSTRACT TRUNCATED AT 250 WORDS)     

Subcutaneous fat in the fetal abdomen as a predictor of growth restriction.

OBJECTIVE: To determine if measuring fetal abdominal fat antenatally using ultrasound can predict fetal growth restriction (FGR). METHODS: One hundred thirty-seven unselected women with singleton pregnancies had serial ultrasound scans at 20, 26, 31, and 38 weeks' gestation. Subcutaneous fat in the fetal abdomen was measured using the same section as the abdominal circumference (AC). Outcome measures were birth weight, neonatal morbidity, and ponderal index. RESULTS: Infants with subcutaneous fat less than 5 mm at 38 weeks (n = 51) were almost five times more likely to have a birth weight below the 10th centile than those with subcutaneous fat of 5 mm or more (n = 75). The incidence of neonatal morbidity was significantly higher in infants with subcutaneous fat less than 5 mm, compared with those with subcutaneous fat of 5 mm or more (20% versus 8%, P < .05). Decreased subcutaneous fat was also associated with a high prevalence of low ponderal index, regardless of birth weight category. CONCLUSION: Measurement of fat in the abdominal wall is a simple technique with a sensitivity for predicting low birth weight similar to that of conventional sonography and might potentially predict FGR irrespective of fetal weight.     

Head circumference/abdominal circumference ratio, ponderal index and fetal malnutrition. Should head circumference/abdominal circumference ratio be abandoned?

Head circumference/abdominal circumference (HC/AC) ratios of the fetus are accepted as a means of distinguishing different patterns of growth retardation with a high ratio implying malnutrition of the fetus. Ponderal index (birthweight/length3) is used by paediatricians as a measure of neonatal wasting and would therefore be expected to correlate with HC/AC ratios at delivery. Anthropometric data on 999 newborn infants have been collected and analyzed by multiple regression. The results show a poor correlation between ponderal index and HC/AC ratio, worse than that between ponderal index and AC alone. The use of HC/AC ratios antenatally to identify subgroups of intrauterine malnutrition should be abandoned. The prediction of intrauterine malnutrition by weight/length ratios should be investigated further.     

Head circumference/abdominal circumference ratio, ponderal index and fetal malnutrition. Should head circumference/abdominal circumference ratio be abandoned?

Summary. Head circumference/abdominal circumference (HC/AC) ratios of the fetus are accepted as a means of distinguishing different patterns of growth retardation with a high ratio implying malnutrition of the fetus. Ponderal index (birthweight/length³) is used by paediatricians as a measure of neonatal wasting and would therefore be expected to correlate with HC/AC ratios at delivery. Anthropometric data on 999 newborn infants have been collected and analyzed by multiple regression. The results show a poor correlation between ponderal index and HC/AC ratio, worse than that between ponderal index and AC alone. The use of HC/AC ratios antenatally to identify subgroups of intrauterine malnutrition should be abandoned. The prediction of intrauterine malnutrition by weight/length ratios should be investigated further.     

Fetal abdominal circumference rather than fetal femur length/abdominal circumference ratio predicts fetal malnutrition in high risk pregnancies

The aim of this study was to compare the ability of abdominal circumference (AC) and fetal femur length/abdominal circumference ratio (FFL/AC) measured by ultrasound within a period of 2 weeks before birth to predict low birth weight percentile and neonatal signs related to fetal malnutrition. From longitudinal ultrasound measurements in 35 normal pregnancies reference data of AC and FFL was obtained. FFL/AC ratio was constant from 21 weeks until term (mean 20.9, SD 1.2) (figure 1). In 350 risk pregnancies AC standard deviation score (AC-SDS) correlated far better than FFL/AC ratio with the deviation of birth weight from normal (figure 3). Furthermore AC-SDS correlated better with ponderal index (PI) and skinfold thickness (ST) than did FFL/AC ratio. Using cut-off levels on AC-SDS and FFL/AC ratio, which selected about 30% of the population, the sensitivity of AC-SDS in predicting the infant being LGA was 81.8% versus 42.9% using FFL/AC ratio (table II). The prediction of the infant being SGA was not improved when the change in AC-SDS or FFL/AC over the last 6-8 weeks of pregnancy was considered. We conclude that AC-SDS correlates well with birth weight deviation and predicts the infant being SGA with a precision equal to the best results reported in the literature, and that FFL/AC ratio is unreliable even when GA is not known because of a high false positive rate.     

Neonatal morphometrics and perinatal outcome: who is growth retarded?

To evaluate the relationship between neonatal morphometrics and poor neonatal outcome resulting from fetal malnutrition, we prospectively examined 355 sequential live-born, singleton neonates greater than 35 weeks' gestational age. Birth weight, neonatal ponderal index, and midarm circumference to head circumference ratio were measured. A birth weight, ponderal index, or midarm circumference to head circumference ratio less than or equal to tenth or greater than or equal to ninetieth percentiles for gestational age was considered abnormal. Poor outcome was defined as operative delivery for fetal distress, 5-minute Apgar score less than 7, meconium aspiration, polycythemia, or hypoglycemia. Thirty-three (9.3%) neonates had perinatal morbidity. Although morbidity was not increased among neonates that were large by any of the criteria, five (25%) of 20 with low birth weight had poor outcome and 18 (26%) of 70 with low ponderal index or midarm circumference to head circumference ratio suffered morbidity. Of the 33 neonates with morbidity, 18 (54.5%) had low ponderal index or midarm circumference to head circumference ratio, but only five (15.2%) had low birth weight. Therefore, low ponderal index and midarm circumference to head circumference ratio are more sensitive predictors of outcome than is birth weight. As such, ponderal index and midarm circumference to head circumference ratio are more appropriate end points for antenatal diagnostic studies than is birth weight.     

Comparison of customized and cohort-based birthweight standards in identification of growth-restricted infants in GUSTO cohort study

Background: The aim was to evaluate the ability of customized and cohort birthweight standards in discriminating intrauterine growth retardation (IUGR).

Methods: Birthweights (BWs) of GUSTO singleton infants born at gestational age (GA) 35–41 weeks were converted using two standards: (a) GUSTO cohort-based BW centile adjusted for GA and baby gender; (b) customized BW percentile calculator adjusted for maternal height and weight, race, parity, GA and gender. Infants were classified into three groups: (1)?<?10th BW centile by customization– customized-SGA, (2)?<?10th BW centile by GUSTO– GUSTO-SGA; and (3)?>?10th BW centile by both standards – BOTH-non-SGA.

Results: Of the 1011 infant–mother dyads, 68 were customized-SGA and 104 were GUSTO-SGA, with concordance of 61% (n?= 63) for SGA. While 5 (7%) of customized-SGA were not SGA by GUSTO-charts, 41 (39%) of GUSTO-SGA were not SGA by customized-charts. Customized-SGA had significantly the least growth in abdominal circumference (AC) and highest head circumference (HC): AC growth ratio between second and third trimester; and the lowest mean BW, ponderal index and placental weight than other groups.

Conclusion: Customized-SGA standard was a better discriminator of pathologic fetal growth based on AC growth. It improved strength of association with pathology and in our population reduced false positives (41/104?=?39%) in the assessment of SGA.     

Value of fetal ponderal index in predicting growth retardation

Fetal ponderal indexes were calculated by ultrasound examination and compared with the neonatal ponderal indexes in 113 pregnancies. The relationship between the fetal and neonatal ponderal indexes throughout gestation is described. The fetal ponderal index also was evaluated as a predictor of intrauterine growth retardation (IUGR) and was found to have sensitivity and specificity of 76.9 and 82%, respectively. These data suggest that the fetal ponderal index could be used to rule out the diagnosis of IUGR with reasonable accuracy (negative predictive value 96.4%).     

The performance of a simple scoring system screening for low birthweight infants for gestation in an unselected pregnant population

Identification of poor fetal growth is an important objective of antenatal care. We evaluated the validity of the Wennergren score to predict small for gestational age and/or underweight for length infants (low ponderal index). To 405 randomly chosen pregnant women from our university hospital population, this numerical scoring system was applied at 28 and 34 weeks of gestation. Birthweights below the 2.3rd and 10th centile and ponderal indexes below the 3rd and 10th centile were used as outcome standards. The sensitivity of predicting SGA infants ranged from 28.4% for infants below the 10th birthweight centile at 28 weeks, to 66.7% for infants below the 2.3rd centile at 34 weeks. Figures for low ponderal indices ranged from 25.0% to 50.0%. In contrast to the promising performance of the Wennergren score as described in the Scandinavian literature, this score was not useful as a screening test for SGA or underweight for length infants in a Dutch hospital population.     

Evidence of growth retardation in neonates of apparently normal weight.

The aim of this study was to examine the relationship of ponderal index (PI) and the ratio of mid-arm circumference to occipito-frontal circumference (MAC/OFC) to the delivered weight of the child. Measurements were made on 160 singleton neonates with birthweight greater than 2500 g and delivery at 37 weeks or more. Surprisingly, there was a highly significant correlation between PI and birthweight and MAC/OFC and birthweight. We conclude that: (1) values of PI must be evaluated in relation to birthweight, and not against a single absolute standard for the whole normal population; (2) measurement of PI and MAC/OFC may reveal a group of growth-retarded infants amongst infants of apparently 'normal' birthweight; and (3) this group of infants might be a target for the extra care normally accorded to the low birthweight infant.     

B型超声测量胎儿股骨皮下组织厚度预测胎儿体重

目的探讨应用Ｂ型超声测量胎儿股骨皮下组织厚度预测胎儿出生体重的临床价值。方法应用Ｂ型超声对１７８例胎儿的双顶径、头围、腹围、股骨长、股骨皮下组织厚度进行测量并与新生儿出生体重的关系进行分析。结果股骨皮下组织厚度与新生儿出生体重相关性最好（ｒ＝０．８６０１）,对巨大儿诊断的敏感性为９１％,特异性为９４％,胎儿股骨皮下组织厚度与孕周呈正相关（ｒ＝０．７０７０）。结论应用Ｂ型超声测量胎儿股骨皮下组织厚度预测胎儿出生体重,方法简单、准确,有较好的临床应用价值。     

Interval between fetal measurements in predicting growth restriction

OBJECTIVE: To determine the influence of the interval between fetal measurements on performance of fetal growth velocity for predicting infants with anthropometric features of fetal growth restriction (FGR). METHODS: Two hundred seventy-four low-risk women had serial fetal biometry at scheduled intervals. Growth velocity of the fetal abdominal area for each was calculated with 2-, 4-, and 6-week scan intervals in which the second measurement was the last scan before delivery. Fetal abdominal area velocity over a 4-week interval in the early third trimester also was included. Fetal growth restriction was defined as skinfold thickness under the tenth percentile, ponderal index under the 25th percentile, midarm circumference-to-occipitofrontal circumference ratio of under -1 standard deviation (SD). Test performance was expressed as likelihood ratios with 95% confidence intervals (CI). RESULTS: Fetal abdominal area velocity calculated over a 4-week interval predicted FGR with a likelihood ratio of 10.4 (95% CI 3.9, 26) for skinfold thickness; 9.5 (95% CI 4.6, 19) for ponderal index; and 4.7 (2.3, 8.4) for midarm circumference-to-occipitofrontal circumference ratio. Intermeasurement intervals of 6 weeks had a likelihood ratio of 8.5 (95% CI 4, 17) for skinfold thickness; 7.5 (95% CI 3.4, 16.1) for ponderal index; and 14 (6.7, 28) for midarm circumference-to-occipitofrontal circumference ratio. The likelihood ratios for the 2-week interval and the early third trimester 4-week interval were all less than 5. CONCLUSION: Four- and 6-week measurement intervals were useful for predicting infants with FGR and were superior to a 2-week interval. Fetal growth velocity is influenced by proximity of the last fetal measurement to date of delivery, which adversely affects clinical use of growth velocity for predicting FGR.     

Neck Circumference Measurements in Second Trimester Fetuses with Down's Syndrome

Ultrasound examinations were performed on 132 normal fetuses between 12 and 25 weeks of gestation to measure the fetal neck circumference (NC), biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), and femur length (FL). The relationships between the fetal neck circumference and gestational age, as well as between the fetal neck circumference and fetal biometric parameters (BPD, HC, AC, FL) were linear. Nomograms between the fetal neck circumference and all other parameters were established including the 5th, 50th, and 95th percentile lines. Only one of nine fetuses with Down's syndrome was found to have abnormally increased fetal neck circumference (above the 95th percentile), whereas the remaining eight cases were equally distributed above and below the 50th percentile of these nomograms. The positive predictive value of an abnormally increased fetal neck circumference was 1.6% in our tested population, where the prevalence of Down's syndrome was 1 in 132. Our observations suggest that the use of fetal neck circumference in second trimester fetuses does not add in the prenatal diagnosis of Down's syndrome.     

B超测量胎儿肝脏面积预测巨大儿的临床价值

目的 :研究应用B型超声测量胎儿肝脏面积预测巨大儿的临床价值。方法 :应用B型超声测量 36 0例足月妊娠胎儿的双顶径、头围、腹围、股骨长度、股骨皮下组织厚度、肝脏长度和肝脏面积 ,并分析各预测指标与新生儿出生体重的关系及用于预测巨大儿的敏感性和特异性。结果 :各项预测指标中胎儿肝脏面积与新生儿体重的相关性最好 (r =0 .80 6 ) ,对巨大儿诊断的敏感性为 88 89% ,特异性为 95 4 2 %。结论 :应用B型超声测量胎儿肝脏面积预测巨大儿的准确性较高 ,具有临床应用价值     

Placental nutrient transfer capacity and fetal growth

The objective of this study was to determine whether the ability of the human placenta to transfer glucose and fatty acids is related to normal fetal growth. The intrinsic nutrient transport capacity of the placenta was measured under standardized conditions during in vitro perfusion of 30 human term placentas and related to birth weight (range 2640-4640g), birth weight centile (8th-99th), ponderal index (2.43-3.69), placental weight (418-1030g) and placental:fetal weight (0.14-0.31). There was no statistically significant change in the rate of nutrient transfer per placenta or per kg fetal weight, with birth weight, birth weight centile, ponderal index, placental weight and placental:fetal weight. There was a weak but significant relationship (P=0.020, r(2)=9 per cent) between the ratio of glucose to fatty acid transport and birth weight centile, largely due to the high ratio found in the lowest birth weight quartile where the babies are thinnest. This study provides no evidence that placental nutrient transport capacity limits fetal growth across a wide range of birth weights in normal pregnancies. It is proposed that the fetus itself may regulate placental nutrient transport in vivo via the fetal cardiac output and the rate of fetal nutrient utilization.     

Fetal umbilical artery velocity waveforms and subsequent neonatal outcome

Summary. Flow velocity waveforms (FVWs) from the fetal umbilical artery were recorded from 2178 pregnant women over a 6-year period. All of them had an obstetric factor indicating increased risk of fetal compromise. A total of 6749 studies was recorded. The systolic diastolic (AB) ratio was measured and classified as normal (<95th centile), elevated (95–99th centile), high (>99th centile) or extreme (absent diastolic flow). The results of these studies have been related to subsequent fetal and neonatal outcome. An abnormal umbilical artery FVW was associated with shorter gestation and infants with lower birthweight, shorter length and lower ponderal index. There was a highly significant association between an abnormal FVW and the birth of an infant small for gestational age. The significance of the association increased with the increased abnormality of the umbilical artery FVW and this was independent of gestational age. Preterm infants associated with high or extreme AB ratios spent twice as long in the neonatal nursery than those with normal AB ratios. Analysis of 794 pregnancies studies serially indicated that an abnormal FVW in which the AB ratio was increasing, in contrast to a decreasing AB ratio, predicted a poor outcome for both size at birth and duration of neonatal intensive care. We conclude that in high risk pregnancy Doppler umbilical artery FVW studies predict the most compromised fetuses in terms of growth retardation and requirements for neonatal intensive care.     

Fetal umbilical artery velocity waveforms and subsequent neonatal outcome

Flow velocity waveforms (FVWs) from the fetal umbilical artery were recorded from 2178 pregnant women over a 6-year period. All of them had an obstetric factor indicating increased risk of fetal compromise. A total of 6749 studies was recorded. The systolic diastolic (AB) ratio was measured and classified as normal (less than 95th centile), elevated (95-99th centile), high (greater than 99th centile) or extreme (absent diastolic flow). The results of these studies have been related to subsequent fetal and neonatal outcome. An abnormal umbilical artery FVW was associated with shorter gestation and infants with lower birthweight, shorter length and lower ponderal index. There was a highly significant association between an abnormal FVW and the birth of an infant small for gestational age. The significance of the association increased with the increased abnormality of the umbilical artery FVW and this was independent of gestational age. Preterm infants associated with high or extreme AB ratios spent twice as long in the neonatal nursery than those with normal AB ratios. Analysis of 794 pregnancies studies serially indicated that an abnormal FVW in which the AB ratio was increasing, in contrast to a decreasing AB ratio, predicted a poor outcome for both size at birth and duration of neonatal intensive care. We conclude that in high risk pregnancy Doppler umbilical artery FVW studies predict the most compromised fetuses in terms of growth retardation and requirements for neonatal intensive care.     

单项超声测量指标预测胎儿体重的临床应用

目的：探讨应用胎儿腹围单项超声测量指标预测胎儿出生体重的临床价值。方法：（１）应用Ｂ型超声对３００例胎儿的腹围、小脑横径、双顶径、股骨长进行测量，并与新生儿出生体重的关系进行分析。经单元线性回归得出腹围预测胎儿体重的单元方程式。（２）应用此方程对３３０例胎儿进行前瞻性验证。结果：腹围与新生儿体重的相关性最好，（ｒ＝０．８６６７９）。依据腹围可以初步预测胎儿出生的体重范围。其符合率达８０．０％。结论：应用超声测量胎儿腹围预测出生体重，方法简单，且较准确，有较好的临床实用价值。