Estimation of gestational age from measurements of fetal long bones

Fetal Humeral Diaphyseal Length in the Second Trimester - A Radiographic Observational Study among Indian Population

Objectives

The present study was performed to provide a normal reference range for humerus diaphysis length at the second trimester of pregnancy in an Indian population.

Materials and Methods

This cross-sectional study was performed on 25 radiographs of aborted normal human fetuses of gestational age (GA) between 13th and 28th weeks. The radiographs were used to measure the maximum length of the humerus using a vernier calliper. Data were collected, tabulated, and statistically analyzed.

Results

The mean diaphyseal length of humerus at the fourth lunar month was 22.18 ± 6.59 mm, and at the seventh lunar month, it was 41.39 ± 10.08 mm. Simple linear regression analysis shows a strongly significant linear relationship of humerus length with GA, biparietal diameter, head circumference, and abdomen circumference.

Conclusion

We have provided a normal reference range for humerus diaphysis length at the second trimester of pregnancy in an Indian population.

Humeral Length versus Femur Length for Estimating Fetal Age in the Third Trimester Using Ultrasound among Saudi Fetuses

Background

Ethnicity can influence organ measurements, so each ethnicity should provide normal references. The study was conducted to measure the normal ranges of humeral and femoral diaphysis lengths, to compare them during the third trimester of pregnancy in the Saudi population, and to identify their role in estimating fetal age.

Methods

This cross-sectional study was conducted among 60 normal singleton pregnant females in the third trimester. The fetal humeral length (HL) and femur length (FL) were taken during ultrasound scanning for follow-up. The IBM Statistical Package for the Social Sciences Version 23 was used to summarize the data and to compare both the lengths with the last menstrual period (LMP) using Pearson's correlation. The comparison was considered statistically significant if P < 0.05.

Results

The mean humeral and femoral diaphysis lengths ± standard deviations were 4.84 ± 1 cm and 5.54 ± 1.2 cm, respectively. A positive linear correlation was present between the length and LMP. The correlation of HL with LMP (r = 0.828) was higher than that of FL with LMP (r = 0.770). HL and FL were correlated. They showed a Pearson's coefficient of 0.941. The study revealed that gender does not affect fetal HL and FL.

Conclusion

Normal reference ranges for femur and humeral diaphysis lengths during the third trimester were provided. The humerus can be used to assess fetal age. Humerus and femur were correlated to each other among Saudi fetuses. Another study with a larger sample size is recommended.

Guideline No. 388-Determination of Gestational Age by Ultrasound

OBJECTIVE

To assist clinicians in assigning gestational age based on ultrasound biometry.

OUTCOMES

To determine whether ultrasound dating provides more accurate gestational age assessment than menstrual dating with or without the use of ultrasound. To provide maternity health care providers and researchers with evidence-based guidelines for the assignment of gestational age. To determine which ultrasound biometric parameters are superior when gestational age is uncertain. To determine whether ultrasound gestational age assessment is cost effective.

EVIDENCE

Published literature was retrieved through searches of PubMed or MEDLINE and The Cochrane Library in 2013 using appropriate controlled vocabulary and key words (gestational age, ultrasound biometry, ultrasound dating). Results were restricted to systematic reviews, randomized control trials/controlled clinical trials, and observational studies written in English. There were no date restrictions. Searches were updated on a regular basis and incorporated in the guideline to July 31, 2013. Grey (unpublished) literature was identified through searching the websites of health technology assessment and health technology-related agencies, clinical practice guideline collections, clinical trial registries, and national and international medical specialty societies.

VALUES

The quality of evidence in this document was rated using the criteria described in the Report of the Canadian Task Force on Preventive Health Care (Table 1).

BENEFITS, HARMS, AND COSTS

Accurate assignment of gestational age may reduce post-dates labour induction and may improve obstetric care through allowing the optimal timing of necessary interventions and the avoidance of unnecessary ones. More accurate dating allows for optimal performance of prenatal screening tests for aneuploidy. A national algorithm for the assignment of gestational age may reduce practice variations across Canada for clinicians and researchers. Potential harms include the possible reassignment of dates when significant fetal pathology (such as fetal growth restriction or macrosomia) result in a discrepancy between ultrasound biometric and clinical gestational age. Such reassignment may lead to the omission of appropriate-or the performance of inappropriate-fetal interventions.

SUMMARY STATEMENTS

RECOMMENDATIONS.

A prospective blinded comparison of second trimester fetal measurements by expert and novice readers using low-cost novice-acquired 3D volumetric ultrasound

RATIONALE AND OBJECTIVES

Two-dimensional (2D) ultrasound (US) is operator dependent, requiring operator skill and experience to selectively identify and record planes of interest for subsequent interpretation. This limits the utility of US in settings in which expert sonographers are unavailable. Three-dimensional (3D) US acquisition of an anatomic target, which enables reconstruction of any plane through the acquired volume, might reduce operator dependence by providing any desired image plane for interpretation, without identification of target planes of interest at the time of acquisition. We applied a low-cost 3DUS technology because of the wider potential application compared with dedicated 3DUS systems. We chose second trimester fetal biometric parameters for study because of their importance in maternal-fetal health globally. We hypothesized that expert and novice interpretations of novice-acquired 3D volumes would not differ from each other nor from expert measurements of expert-acquired 2D images, the clinical reference standard.

MATERIALS AND METHODS

This was a prospective, blinded, observational study. Expert sonographers blinded to 3DUS volumes acquired 2DUS images of second trimester fetuses from 32 subjects, and expert readers performed interpretation, during usual care. A novice sonographer blinded to other clinical data acquired oriented 3DUS image volumes of the same subjects on the same date. Expert readers blinded to other data assessed placental location (PL), fetal presentation (FP), and amniotic fluid volume (AFV) in novice-acquired 3D volumes. Novice and expert raters blinded to other data independently measured biparietal diameter (BPD), humerus length (HL), and femur length (FL) for each fetus from novice-acquired 3D volumes. Corresponding gestational age (GA) estimates were calculated. Inter-rater reliability of measurements and GAs (expert 3D versus expert 2D, novice 3D versus expert 2D, and expert 3D versus novice 3D) were assessed by intraclass correlation coefficient (ICC). Mean inter-rater measurement differences were analyzed using one-way ANOVA.

RESULTS

3D volume acquisition and reconstruction required mean 30.4 s (±5.7) and 70.0 s (±24.0), respectively. PL, FP, and AFV were evaluated from volumes for all subjects; mean time for evaluation was 16 s (±0.0). PL, FP, and AFV could be evaluated for all subjects. At least one biometric measurement was possible for 31 subjects (97%). Agreement between rater pairs for a composite of all measures was excellent (ICCs ≥ 0.95), and for individual measures was good to excellent (ICCs ≥ 0.75). Inter-rater differences were not significant (p > .05).

CONCLUSIONS

Expert and novice interpretations of novice-acquired 3DUS volumes of second trimester fetuses provided reliable biometric measures compared with expert interpretation of expert-acquired 2DUS images. 3DUS volume acquisition with a low-cost system may reduce operator dependence of ultrasound.

Fetal Anthropometric Features: A Postmortem Study of Fetuses After the Termination of Pregnancy for Psychosocial Reasons Between 12 and 20 Gestational Weeks

INTRODUCTION

Reference ranges in fetal postmortem anthropometric data derive from heterogeneous studies and rely on data obtained after intrauterine fetal death and abortion, which may introduce bias in the reported fetal growth parameters. We report anthropometric findings in fetuses with the least variation due to cause of death or developmental anomalies.

METHODS

We analyzed fetuses after the termination of pregnancy for psychosocial reasons. The external measurements, X-ray dimensions, and body and organ weights were recorded as well as the placenta weight. A thorough and standardized postmortem analysis allowed the design of 2 different groups. Group 1 was composed of fetuses (1) born to mothers with no relevant obstetrical history, (2) no X-ray anomaly, (3) no abnormal autopsy findings, and (4) unremarkable placenta histology. An anomaly in any of these 4 entities moved the fetuses to Group 2. For reference ranges and graph construction, a well-designed statistical methodology was applied.

RESULTS

A total of 335 fetuses were analyzed during an 11-year period. Group 1 comprised 232 fetuses aged 12 to 20 gestational weeks, whereas 103 fetuses were considered in Group 2. Comparison between the 2 groups showed almost no differences. Only the Group 1 results were submitted to statistical analysis, and reference ranges and graphs were constructed.

CONCLUSIONS

To the best of our knowledge, we provide in this study the first anthropometric references established from almost normal fetuses, albeit for a limited fetal timeframe.

Détermination de l'âge gestationnel par échographie

OBJECTIF

Aider les cliniciens à attribuer un âge gestationnel en fonction des résultats de la biométrie échographique.

ISSUES

Déterminer si la datation par échographie offre une évaluation plus précise de l'âge gestationnel que la datation en fonction des dernières règles avec ou sans recours à l'échographie. Offrir, aux praticiens et aux chercheurs du domaine des soins de maternité, des lignes directrices factuelles en matière d'attribution de l'âge gestationnel. Identifier les paramètres biométriques échographiques qui sont de fiabilité supérieure lorsque l'âge gestationnel est incertain. Déterminer la rentabilité de l'évaluation de l'âge gestationnel par échographie. RéSULTATS: La littérature publiée a été récupérée par l'intermédiaire de recherches menées dans PubMed ou MEDLINE et The Cochrane Library en 2013 au moyen d'un vocabulaire contrôlé et de mots clés appropriés (p. ex. « gestational age », « ultrasound biometry » et « ultrasound dating »). Les résultats ont été restreints aux analyses systématiques, aux essais comparatifs randomisés / essais cliniques comparatifs et aux études observationnelles rédigés en anglais. Aucune restriction n'a été appliquée en matière de dates. Les recherches ont été mises à jour de façon régulière et intégrées à la directive clinique jusqu'au 31 juillet 2013. La littérature grise (non publiée) a été identifiée par l'intermédiaire de recherches menées dans les sites Web d'organismes s'intéressant à l'évaluation des technologies dans le domaine de la santé et d'organismes connexes, dans des collections de directives cliniques, dans des registres d'essais cliniques et auprès de sociétés de spécialité médicale nationales et internationales.

VALEURS

La qualité des résultats est évaluée au moyen des critères décrits dans le rapport du Groupe d'étude canadien sur les soins de santé préventifs (Tableau 1). AVANTAGES, DéSAVANTAGES ET COûTS: L'attribution précise d'un âge gestationnel pourrait réduire l'incidence du déclenchement mené en raison d'une grossesse prolongée et améliorer les soins obstétricaux en nous permettant de planifier la chronologie des interventions nécessaires de façon optimale et d'éviter les interventions inutiles. Une datation plus précise permet l'optimisation de la tenue de tests prénataux de dépistage de l'aneuploïdie. Un algorithme national d'attribution de l'âge gestationnel pourrait atténuer les variations pancanadiennes en matière de pratique pour les cliniciens et les chercheurs. Parmi les désavantages potentiels, on trouve la réattribution possible des dates lorsqu'une pathologie fœtale importante (comme le retard de croissance intra-utérin ou la macrosomie) donne lieu à une divergence entre les résultats de la biométrie échographique et l'âge gestationnel clinique. Une telle réattribution pourrait mener à l'omission d'interventions fœtales justifiées ou à la tenue d'interventions fœtales injustifiées. DéCLARATIONS SOMMAIRES: RECOMMANDATIONS.

Embryonic Heart Rate and Age

This study used linear regression analysis to show that embryonic heart rate (EHR) can be used in the clinical setting to provide an estimate of embryonic age that correlates well with the fetal crown-rump length age (CRL; r = 0.856). A regression was performed on data from 275 examinations in which an embryonic heart rate was recorded before the ninth menstrual week from a cross-sectional population of 1,136 examinations throughout pregnancy. In this analysis, EHR was used as the independent variable and CRL as the dependent variable to yield the following formula for CRL age in menstrual days: CRL Age (menstrual days) = 8.18 + 0.285 EHR. Based on this result, a rounded version of the formula was sought that would provide essentially the same estimated fetal age as the regression formula for the range of EHR that occurred in the sample (84-193 beats/min) yet allow for a simpler computation. Within that range of EHR, the following clinical versions of the regression formula were found to produce results that did not differ significantly from the original formula: Days of Gestation = 0.3 EHR -8 and Menstrual Days Age = 0.3 EHR + 6. Both the original regression and the clinical versions yielded 95% prediction intervals of approximately ± 8 days across the range of EHR that occurred in the sample. While fetal age based on this method is only an approximation of the CRL age, the heart rate can be obtained using time/motion mode sonography when only the less accurate gestational sac diameters are available. The EHR is useful to corroborate early age estimates, especially when using transvaginal transducers and may provide useful information concerning cardiac development.

Normal Fetal Growth Assessment: A Review of Literature and Current Practice

A review of literature and current practice of normal fetal growth assessment is presented. Ultrasonographic dating of pregnancy in the first, second, and third trimester is reviewed. Individual biometric parameters are examined, and the proper use of the fetal growth profile is explained. Use of this information is discussed as it pertains to the single pregnancy.

Estimation of gestational age from gall-bladder length

Establishing a precise duration of gestation is vital in situations such as infanticide and criminal abortions. The present study attempted to estimate the gestational age of the foetus from gall-bladder length. Foetuses of various gestational age groups were dissected, and the length of the gall bladder was measured. The results were analysed, and a substantial degree of correlation was statistically confirmed. This novel method is helpful when the foetus is fragmented, putrefied or eviscerated, where this method can be used as an additional parameter to improve the accuracy of foetal age estimation.

Using the petrous part of the temporal bone to estimate fetal age at death

Little is understood about the age-related changes in the petrous part of the temporal bone in fetal life. The purposes of this study were to examine documented skeletal remains of Japanese fetuses, to measure the length of the petrous part, and to develop diagnostic standards for fetal age-at-death estimation that could be applied to poorly preserved skeletons. The results indicated that it is possible to use a regression equation to estimate age at death directly from the length of the petrous part of the temporal bone. The application of the present method to a different population led to a fetal age-at-death estimation with an error of less than 1 month. We also used the Bayesian estimation, which yielded posterior probabilities of age, conditional on being of a particular length of the petrous part. The reference table of estimated gestational age may provide an easy-to-use indicator of the fetal age at death. In conclusion, measurement of the petrous part of the temporal bone may offer a new methodological basis for forensic and bioarchaeological diagnoses of fetuses.

Two-dimensional sonographic placental measurements in the prediction of small-for-gestational-age infants

OBJECTIVES

To determine the utility of two-dimensional (2D) sonographic placental measurements in the prediction of small-for-gestational-age (SGA) infants.

METHODS

The maximal diameter along the fetal surface of the placenta and the maximal placental thickness were measured at 18-24 weeks' gestation, and the measurements repeated in the orthogonal plane. 'Biometric lags' were calculated as the difference between sonographic gestational age, estimated using each of a number of fetal biometric measurements, and actual gestational age. These variables were analyzed individually and in combination as predictors of birth weight<10(th) percentile (SGA<10) and <5(th) percentile (SGA<5).

RESULTS

1909 singleton pregnancies were included. Mean placental diameter (SGA<10, P<0.001; SGA<5, P=0.002) and thickness (SGA<10, P<0.006; SGA<5, P=0.065) were significantly smaller in SGA pregnancies. The biometric lags were greater in SGA pregnancies, the lag in abdominal circumference (AC) being the most predictive of SGA (P<0.0001). Multivariable models were significantly predictive of both SGA<10(th) percentile (area under the receiver-operating characteristics curve (AUC) =0.7404) and <5(th) percentile (AUC=0.7204), the best fitting models including AC lag and mean placental diameter and thickness.

CONCLUSIONS

2D placental measurements taken in mid-gestation are significantly associated with the incidence of SGA. Biometric lags can improve the predictive ability further. These easily obtained variables should be considered in future efforts to develop a clinically useful predictive model for adverse outcome of pregnancy.

Normal ranges for fetal femur and humerus diaphysis length during the second trimester in an Iranian population

OBJECTIVES

Shortening of the fetal long bones is a sonographic soft marker for screening of Down syndrome in the second trimester that can be influenced by ethnicity. The purpose of this study was to provide normal reference ranges for femur and humerus diaphysis length during the second trimester of pregnancy in an Iranian population.

METHODS

This cross-sectional study was performed on 3011 singleton fetuses at 15 to 28 weeks' menstrual age. The relationship between menstrual age and both femur and humerus diaphysis length was determined, and percentile values for each menstrual week were provided.

RESULTS

The median femur diaphysis length ranged from 18.05 mm at 15 menstrual weeks to 52.20 mm at 28 menstrual weeks, and the mean humerus diaphysis length ranged from 17.65 mm at 15 menstrual weeks to 48.10 mm at 28 menstrual weeks. There was a linear relationship between menstrual age and both femur diaphysis length (R² = 0.957) and humerus diaphysis length (R² = 0.941).

CONCLUSIONS

We have provided normal reference ranges for femur and humerus diaphysis length during the second trimester of pregnancy in an Iranian population.

Early biometric lag in the prediction of small for gestational age neonates and preeclampsia

OBJECTIVE

An early fetal growth lag may be a marker of future complications. We sought to determine the utility of early biometric variables in predicting adverse pregnancy outcomes.

METHODS

In this retrospective cohort study, the crown-rump length at 11 to 14 weeks and the head circumference, biparietal diameter, abdominal circumference, femur length, humerus length, transverse cerebellar diameter, and estimated fetal weight at 18 to 24 weeks were converted to an estimated gestational age using published regression formulas. Sonographic fetal growth (difference between each biometric gestational age and the crown-rump length gestational age) minus expected fetal growth (number of days elapsed between the two scans) yielded the biometric growth lag. These lags were tested as predictors of small for gestational age (SGA) neonates (≤10th percentile) and preeclampsia.

RESULTS

A total of 245 patients were included. Thirty-two (13.1%) delivered an SGA neonate, and 43 (17.6%) had the composite outcome. The head circumference, biparietal diameter, abdominal circumference, and estimated fetal weight lags were identified as significant predictors of SGA neonates after adjusted analyses (P < .05). The addition of either the estimated fetal weight or abdominal circumference lag to maternal characteristics alone significantly improved the performance of the predictive model, achieving areas under the curve of 0.72 and 0.74, respectively. No significant association was found between the biometric lag variables and the development of preeclampsia.

CONCLUSIONS

Routinely available biometric data can be used to improve the prediction of adverse outcomes such as SGA. These biometric lags should be considered in efforts to develop screening algorithms for adverse outcomes.

Nontraditional sonographic pearls in estimating gestational age

Accurate gestational dating is one of the most important assessments obstetrical providers make in pregnancy, given that all of the various management strategies are dependent on knowing where the patient is in gestation. In addition to traditional biometry, ancillary biometric and nonbiometric measurements can help narrow the biologic variability between fetuses. Moreover, one can employ these nontraditional measurements both in late gestation to assist in determining appropriate gestational age and fetal lung maturity, and in other specific clinical situations-such as oligohydramnios, in which compression of the fetal head and abdomen can lead to difficulty in obtaining an accurate biparietal diameter and abdominal circumference. This chapter focuses on nontraditional fetal ultrasound measurements, including the transverse cerebellar diameter, fetal foot length, ratios of biometric and nonbiometric measurements, epiphyseal ossification centers, amniotic fluid volume, placental grading, and other miscellaneous markers in the context of evaluating a fetus with possible intrauterine growth restriction.

Fetal age assessment based on femur length at 10-25 weeks of gestation, and reference ranges for femur length to head circumference ratios

BACKGROUND

The aim of the present study is to establish new reference charts for gestational age assessment based on fetal femur length (FL), and new reference ranges for FL to head ratios at gestational weeks 10-25, and to determine the effect of maternal and fetal factors on these charts.

METHODS

Six hundred fifty low-risk women with regular menstrual periods and singleton pregnancies were recruited to a prospective cross-sectional study after obtaining written consent. FL, outer-outer biparietal diameter (BPD), and head circumference (HC) were measured at 10-25 weeks of gestation. We used regression analysis in order to construct mean curves and to assess the effect of maternal and fetal factors on age assessment.

RESULTS

The new chart for age assessment by means of FL was based on 636 measurements. The 95% CI of the mean corresponded to <1 day. The variation between the mean and the 90th percentile was 5, 6, and 7 days at 13, 18, and 23 weeks, respectively, similar to the results when using BPD or HC. Maternal age modestly influenced gestational age assessment (1.3 days/10 years, P = 0.005), whereas smoking, height, body mass index, multiparity, fetal sex, cephalic index, and breech presentation had no impact. Reference charts for FL to head ratios have been presented. Maternal age, fetal sex, and cephalic index influenced the FL/BPD ratio, whereas only fetal sex influenced FL/HC.

CONCLUSIONS

Fetal age assessment based on FL is an equally robust method as using HC. FL/HC is a more robust ratio to characterize fetal proportions than is FL/BPD.

Skeletal anomalies

It is possible to identify many types of skeletal dysplasias and conditions involving limb deformities prenatally using ultrasound. It is likely that in the future, with the advancing technology and discoveries in molecular genetics, specific mutation analysis will become available for many of these conditions. This will make first trimester diagnosis an option in many cases. Because of the complex nature of many of these cases, it may be helpful to use a multidisciplinary approach involving a radiologist and a geneticist at times. In utero radiographs may help clarify a diagnosis. In lethal cases where a specific diagnosis has not been confirmed, it may be helpful postpartum to obtain an autopsy; photographs; complete body radiographs; karyotypic analysis; and specimens of bone, cartilage, and fetal blood for further analysis.

Fetal age: methods of estimation and effects of pathology

Accurate identification of fetal age is important in a wide variety of circumstances. Seventeen anthropometric and radiographic measurements were taken on fetuses between 15 and 42 weeks of gestational age, both with and without pathologic conditions. A full evaluation including radiographic, karyotypic, gross anatomic, and histologic examination of the fetus and placenta identified 72 individuals as nondysmorphic with no signs of chronic uterovascular insufficiency. These specimens served as the control group. Based on least-squares regressions of this group, age-estimation equations were calculated for all variables. Six models were adequately described by linear equations; the remaining 11 required a quadratic term. Based on standard error of the estimate (S(y:x)), skeletal measures proved the most accurate age estimators. Pathologic conditions were shown to have an influence on age estimation indicated by high levels of inaccuracy and, in some instances, significant bias.

Prenatal sonographic diagnosis of skeletal dysplasias. A report of 47 cases

The purpose of this study was to evaluate the foetal sonographic efficiency for prenatal diagnosis of osteochondrodysplasias. Forty-seven prenatal and postnatal cases diagnosed between January 1993 and December 1998 in the referral sonographic centres of Strasbourg were studied. All cases were reviewed retrospectively and the prenatal ultrasound findings and diagnosis were compared to the postnatal or post-mortem diagnosis. Each case was studied by ultrasonographers, geneticists, radiologists, and foetopathologists. Final diagnosis was based on clinical examination, skeletal survey and molecular testing as deemed necessary. Routine screening and dating was the indication for foetal sonography in 72% (32/47) of our cases. The most likely time of diagnosis was between 16 and 24 weeks of gestation (17 out of 47 cases, 36%), which corresponds to the time of foetal anomaly sonographic scan in France. The other cluster of cases (12 among 47, 26%) was disclosed before 16 weeks of gestation. These results illustrate the importance of a detailed evaluation of the limbs during sonographic examinations of first and second trimesters of pregnancy. While the identification of skeletal dysplasias was relatively easy in our study, the ability to make an accurate specific antenatal diagnosis was more difficult. An accurate diagnosis was proposed in 28 of the 47 cases (60%). In 19% of the cases (9/47), the prenatal diagnosis was not accurate; in 21% of the cases (10/47), the prenatal diagnosis was imprecise. In 45 of the 47 cases (96%) prenatal foetal scan correctly predicted the prognosis.

Ultrasound assessment of fetal biparietal diameter and femur length during normal pregnancy in Iranian women

OBJECTIVES

To determine the pattern of intrauterine growth and predicted biparietal diameter (BPD) and femur length (FL) at point in gestation of Iranian fetuses.

METHODS

In an extensive and long-standing prospective study in Tehran, Iran 15693 BPD and 15594 FL measurements were obtained from the fetuses of 1324 normal pregnant women. Weekly mean values and the standard deviations (S.D. ) were calculated for both BPD and FL from 12 to 40 weeks of pregnancy. Comparison was also made between our results and previous Western studies using t-test analysis.

RESULTS

Iranian fetuses had smaller BPD and shorter FL measurements in comparison with Western studies (P<0.05). There is a lag in BPD growth of our fetuses. The lag in FL growth is even more than BPD. Growth of the BPD and FL showed an asymptotic curve like that of Western studies but both of our values were lower.

CONCLUSION

Ethnicity may influence ultrasonic fetal biometric measurements.

Inaccuracy of Ballard scores before 28 weeks' gestation. National Institute of Child Health and Human Development Neonatal Research Network

OBJECTIVE

Ballard scores are commonly used to estimate gestational age (GA). The purpose of this study was to determine the accuracy of the New Ballard Score (NBS) for infants <28 weeks GA by accurate menstrual history and to evaluate NBS as an outcome predictor.

METHODS

Infants weighing 401 to 1500 g in 12 National Institute of Child Health and Human Development Neonatal Research Network centers had NBS performed before age 48 hours. Accuracy of NBS estimates of GA was assessed for infants with GA determined by accurate menstrual history. In a larger cohort of infants, NBS was included in regression models of the association of NBS and death, poor outcome, and duration of hospital stay.

RESULTS

At each week from 22 to 28 weeks GA by accurate menstrual history, NBS estimates exceeded GA by dates by 1.3 to 3.3 weeks, and estimates varied widely (range of widths of 95% CIs for the observations, 6.8 to 11.9 weeks). NBS did not contribute significantly to regression models of death, poor outcome, or duration of hospital stay.

CONCLUSIONS

Inaccuracies in GA determined by the NBS should be considered when treating extremely premature infants, particularly in decisions to forego or administer intensive care. Refinement of GA scoring systems is needed to optimize clinical benefit.

Forty years of obstetric ultrasound 1957-1997: from A-scope to three dimensions

In this article, we record the history of obstetric ultrasound as it developed worldwide in the second half of the twentieth century. The technological advances during this period saw the evolution of equipment from the original adapted metal flaw detectors producing a simple A-scan to the modern, purpose built, real-time colour flow machines with three-dimensional capability (Fig. 1). Clinically, ultrasound began as a research tool, but the poor quality of the images led to the ridicule of many of the early investigators. However, because of their perseverance, ultrasound developed into an imaging modality providing immense diagnostic capabilities and facilitating with precision many invasive procedures, diagnostic and therapeutic, both of which have made significant contributions to patient care. In this history, we recall the people, the personalities, and the problems they encountered during the development of ultrasound and how these problems were resolved, so that ultrasound now is available for use in the care of pregnant women throughout the developed world.

How accurate is fetal biometry in the assessment of fetal age?

OBJECTIVE

The purpose of the study was to assess the accuracy of fetal biometry in the midtrimester of pregnancy in the assignment of fetal age.

STUDY DESIGN

A total of 152 singleton, 67 twin, and 19 triplet gestations resulting from in vitro fertilization with ultrasonographic fetal biometry from 14 to 22 weeks made up the study population. A gestational age prediction equation was derived from singletons with the use of stepwise linear regression. This equation was compared with 38 previously published equations and then applied to the twin and triplet populations.

RESULTS

Head circumference was the best predictor of gestational age (random error [SD] 3.77 days). Addition of abdominal circumference and femur length to head circumference improved the accuracy of the dating equation (random error 3.35 days). Most dating formulas had systematic errors of <1 week. The systematic error was -0.32 day for averaging the singleton-based predictions for twins and -1.26 days for triplets.

CONCLUSIONS

Gestational age assessment with the use of fetal biometry from 14 to 22 weeks is accurate for singleton, twin, and triplet gestations.

Growth patterns of the humeral and femur length in a multiethnic population

OBJECTIVES

To study whether there are any differences in growth of the femoral and humeral length between the three major ethnic groups in Malaysia viz Malays, Chinese and Indians. The effect on fetal growth by gender of the baby and parity of the mother was also studied.

METHODS

The setting was the University of Kuala Lumpur. Thirty-four Malay, 35 Chinese and 34 Indian normal pregnant middle-class women were studied longitudinally by monthly ultrasound scans for 18 to 38 weeks of gestation. The data were subjected to regression analysis; the quadratic curve was found to be the most adequate. Dummy variables were used to determine any effects by gender, parity as well as ethnicity on the length of limb growth. There was no difference in birth weights of the three ethnic groups studied, nor in gender or parity.

RESULTS

There were found to be significant differences in limb lengths of the Indians (longer) when compared with the Malays and Chinese. Parity seems to affect only Indians in whom the multiparous fetuses have shorter limb lengths than the primaparous. There appears to be no effect by gender.

CONCLUSION

There appear to be definite differences in growth of limb length between the different Malaysian ethnic groups and this should be taken into account when growth charts are used and when fetal weight formulas are calculated using limb lengths. The limitation of this study was that the numbers of subjects studied were small. Larger studies will be able to confirm or refute the findings.

Ultrasonographic assessment of fetal growth: comparison between human and ovine fetus

OBJECTIVE

Our purpose was to evaluate the rate of ovine fetal growth for several body parameters by serial ultrasonographic measurements and to compare them with analogous data in the human fetus.

STUDY DESIGN

Forty-three ewes with singleton gestations were studied. Four parameters were measured: biparietal diameter, abdominal circumference, femur length, and tibia length. Ultrasonographic examinations were performed weekly from 50 to 138 days of gestation (term 147 days). Quadratic regression analysis was used to describe each data set.

RESULTS

The biparietal diameter showed a significant deceleration of its growth rate. The abdominal circumference showed a linear growth pattern. Both femur and tibia revealed a significant acceleration of the growth rate.

CONCLUSION

The ovine fetal growth pattern is different from that observed in the human fetus, in which all four parameters show deceleration of the growth rate in late gestation. In comparison to the ovine, the human fetus reaches similar abdominal circumference and femur length values at term, but in a gestational period that is twice as long. In sharp contrast to abdominal circumference and femur length growth, the biparietal diameter has a similar growth rate in both species. Thus the human fetus has a slower rate of somatic growth and its greater biparietal diameter at term results from the longer gestational period.

The value of routine early pregnancy ultrasound in the antenatal booking clinic

The value of routine antenatal booking ultrasound as an adjunct to, or as an alternative to the 18 to 20 week ultrasound, is not known. A study into the possible benefits of routine antenatal booking ultrasound was undertaken. One year's experience, involving 1,372 scans is described. The main medical benefits include the establishment or correction of gestational age (41.7% of all pregnancies) and the identification of multiple pregnancies (0.7%), nonviable pregnancies (1.4%) and other pregnancies requiring specialist antenatal clinic referral (0.7%), resulting in a total of 44.5% of patients in whom some benefit was obtained.

Fetal biometry in the Brachmann-de Lange syndrome

The Brachmann-de Lange syndrome (BDLS) is diagnosed in children on the basis of a distinctive clinical phenotype which includes retarded physical growth. Because there are no genetic or biochemical tests at present, the antenatal detection of the syndrome may depend upon identification of some aspect of the phenotype in the fetus using ultrasound imaging. We studied the growth of 23 subsequently diagnosed fetuses with the BDLS using standard biometric parameters defined by prenatal ultrasound imaging. Sonographic studies were obtained through a national parents' group, the Cornelia de Lange Syndrome Foundation. Assessment of fetal growth was made using four standardized measurements: the biparietal diameter, head circumference, femur length, and abdominal circumference. These values were compared to established tables of normal fetal growth and established ratios of fetal body proportions. The cross-sectional growth curve derived using all measurements collected as a composite group indicates that growth retardation would be first detected as early as 25 weeks. In five fetuses with measurements both before and after 25 weeks of gestation, longitudinal growth curves indicated that the diagnosis of "small for gestational age" would have been suggested between 20 and 25 weeks. The mean fetal weight estimates closely followed the fifth centile curve of normal fetuses both before and after 25 weeks. Cephalic indices in BDLS fetuses indicated either frank brachycephaly (25%), or were at the upper portion of the normal range. Femur lengths were relatively short (less than 90% of their expected length) ion 4 of the 11 fetuses where such information could be obtained.(ABSTRACT TRUNCATED AT 250 WORDS)

Routine ultrasound surveillance of the pregnant uterus

The routine ultrasound examination of the pregnant uterus is presented in this article. The approach is based on published guidelines, dividing the examination into studies of the first trimester and studies of the second and third trimesters. The discussion emphasizes the standard anatomical views and describes the normal sonographic appearances. The methods of obtaining important measurements are described, and tables are provided to analyze these measurements. A systematic approach to obstetric ultrasound is important in ensuring completeness and in maximizing the detection of fetal abnormality.

Fetal sacral length in the ultrasonographic assessment of gestational age

OBJECTIVE

Our purpose was to establish a nomogram of fetal sacral length throughout gestation and to assess its value in cases of abnormal fetal growth.

STUDY DESIGN

A prospective cross-sectional study of 506 singleton fetuses with normal growth between 15 and 41 weeks' gestation was performed. Regression analyses were performed on sacral length, gestational age, biparietal diameter, head circumference, and femur length. The sacral length in 80 singleton gestations with abnormal growth (40 > 90th percentile and 40 < 10th percentile for gestational age) were compared with the nomogram.

RESULTS

Linear relationships between gestational age and sacral length, biparietal diameter, head circumference, and femur length were demonstrated. Sacral length (centimeters) as a function of gestational age (weeks) was expressed by the regression equation: Sacral length = -0.108 + 0.102 Gestational age, with a Pearson correlation coefficient of R2 = 0.959. The sacral length of all 80 fetuses with abnormal growth demonstrated the same relationship to gestational age as did the 506 normal controls.

CONCLUSION

This study defines the normal limits of sacral length; demonstrates a high correlation between sacral length, gestational age, and other standard measurements of fetal growth; and indicates that sacral length can predict gestational age, irrespective of fetal nutritional status.

Standardized residuals as a means for detection of growth alteration in the pathologic human fetus

This paper introduces and discusses the use of standardized residuals as a technique for comparing the growth of normal and pathologic human fetuses. Anthropometric measures, radiographic measures, and organ weights were regressed on known gestational age of second- and third-trimester fetuses. Standardized residuals were calculated for a group of potentially growth-impaired fetuses. Use of residuals aids in identification of patterns of growth alteration in specific pathologies. Most important, studying the response of developing organ systems to a variety of insults may elucidate mechanisms of growth regulation in the fetus. We emphasize the special quality of the multivariate measures of the core sample of fetuses from the Akron Children's Hospital collection.

Ultrasonographic detection of the second-trimester fetus with trisomy 18 and trisomy 21

Biparietal diameter/femur length ratio and nuchal thickness were found to be sensitive indicators for the prenatal detection of trisomy 18 and trisomy 21. A biparietal diameter/femur length ratio greater than 1.5 SD above the control mean correctly identified 5 of 11 (46%) fetuses with trisomy 21 and 3 of 4 (75%) fetuses with trisomy 18. Nuchal thickening (6 mm or more) correctly identified 5 of 12 (41%) fetuses with trisomy 21 and 2 of 4 (50%) fetuses with trisomy 18. The sensitivity and specificity of the biparietal diameter/femur length ratio in detecting either aneuploidy was 53% and 93%, respectively, whereas a thickened nuchal fold had a sensitivity of 44% and a specificity of 100%. The combined use of the two ultrasonographic measurements had an overall sensitivity of 81% and a specificity of 93%. Prospective ascertainment of these two trisomies appears warranted in low-risk populations.

Ultrasonographic measurement of fetal femur length in growth disturbances

Ultrasonographic measurement of fetal femur length is a recognized technique for determination of gestational age and fetal growth. A total of 280 pregnant women were studied, each of whom had pathologies with the potential to either accelerate or delay fetal growth. There were 1000 measurements of the fetal femur length performed on these 280 fetuses. A total of 125 fetuses were found to have a growth disturbance-91 with asymmetrical intrauterine growth retardation and 34 with macrosomia. Comparison of fetuses with either intrauterine growth retardation or macrosomia with appropriate-for-gestational-age fetuses showed that the femur length is not statistically affected by intrauterine growth abnormalities.

Fetal radius length: a critical evaluation of race as a factor in gestational age assessment

Growth of the fetal radius was examined ultrasonographically in a prospective cross-sectional study of 290 white and 63 black patients between 12 and 43 weeks' gestation. The mean of radius length and 95% predictive intervals were calculated for each week. The most efficient description of the data was given by a simple log-linear model. The slopes for the white and black study groups estimated were distinctly different. Consequently, a single equation was estimated that considers race when assessing gestational age from radius length.

Fetal foot length--a new parameter for assessment of gestational age

Ultrasonographic measurement of fetal foot length, a new parameter, was correlated with the gestation age. One hundred and five ultrasonographic measurement of fetal foot length was performed between 13 and 42 weeks gestation. Comparison of linear regression of foot length versus gestational age demonstrated a strong correlation with an r2 value of 0.84 (P less than 0.001). Ninety-five percent confidence intervals at each week compared favorably with both biparietal diameter and femur length data. Mean foot lengths at each week of gestation compared favorably with data based on pathological specimens described in 1920 (Streeter GL: Weight, sitting height, head size, foot length and menstrual age of the human embryo. Contrib Embryol Carnegie Inst. 11: 143, 1920). Measurement of fetal foot length is of particular use when other parameters do not accurately predict gestational age, e.g. hydrocephalus, anencephaly, short limb dysplasia. It can also be used in conjunction with biparietal diameter and femur length in the management of patients with premature labor in order to patients with premature labor in order to accurately predict gestational age. Hence the present study demonstrates that the ultrasonographic measurement of foot length is a reliable indicator of gestational age.

Routine perinatal postmortem radiography in a peripheral pathology laboratory

Routine postmortem radiography was done in 234 consecutive perinatal autopsies. Using ossification centre appearance and length of femoral shafts as variable it was a very useful and dependable method for estimating gestational age and intrauterine growth. In this way important conclusions can be drawn as to the reason for intrauterine growth deviations. Also many, sometimes diagnostic, abnormalities can be found.

Fetal foot length as a predictor of gestational age

Ultrasonographic measurement of fetal foot length is useful in the assessment of gestational age. Two hundred twenty-three postpartum and 224 ultrasonographic measurements were performed between 11 and 43 weeks' gestation; 207 postpartum and 160 ultrasonographic measurements met our requirements of secure dates and no physical anomaly or maternal disease. Mean foot length at each week of gestation compared favorably with Streeter's data, based on pathologic specimens, described in 1920. Comparison of curvilinear regression of foot length versus gestational age demonstrated a strong correlation with an R2 value of 0.981; 95% confidence intervals at each week compared favorably with both biparietal diameter and femur length data. Fetal foot length is a reliable parameter for use in the assessment of gestational age and is particularly useful when other parameters do not accurately predict gestational age, for example, hydrocephalus, anencephaly, short limb dysplasia.

The prenatal growth of the human body determined by the measurement of bones and organs by ultrasonography

This paper presents the ultrasonographic analysis of the growth of two groups of human fetuses, one longitudinal and the other cross-sectional. Measurements of all the long bones were taken, as well as measurements of the following diameters: Biparietal, occipitofrontal, thoracic and abdominal anterior/posterior and transverse, spinal canal width, arm, forearm, thigh and leg transverse. The bladder and the stomach were also measured. The pregnancies analyzed covered the period between the 8th and 38th week of gestation. Centiles (3rd-97th) were calculated for each structure and week. All pregnancies known or suspected to be abnormal were removed from the study. The values obtained were tested in 102 pregnancies (test group); the expected values (from the graphs) did not deviate from the values obtained from this group of fetuses, demonstrating the reliability of the values presented in these graphs. All structures measured showed linear growth. There was no significant difference between the longitudinal and cross-sectional groups.

Fetal mucolipidosis II (I-cell disease): radiologic and pathologic correlation

A pregnant woman whose previous child had a diagnosis of I-cell disease was referred for evaluation of the fetus. Fluid obtained by amniocentesis and maternal serum showed abnormally increased levels of lysosomal enzymes suggesting that the fetus had I-cell disease. Sonography at 18 weeks showed abnormally short femurs and intrauterine growth retardation. The pregnancy was electively terminated at 19 weeks' gestation and the diagnosis was confirmed. Radiographs of the fetus demonstrated that the bony dysplasia is present early in fetal life with diffuse decrease in bone mineralization, a coarse, lacy, trabecular pattern, overall shortening and under-modelling of the long bones, subperiosteal bone deficiency in the diaphysis giving the appearance of periosteal new bone, hypoplasia of the anterior superior aspect of the upper lumbar vertebral bodies, broad ribs, abnormal pelvis with squared iliac wings and flattened acetabular roofs, and a small irregular calcaneal ossification center. There was good correlation between the radiographic findings and the microscopic findings in the bones. We observed deficient endosteal bone formation, small epiphyses, and poorly developed intervertebral discs. We speculate that this indicates impaired production of extra-cellular matrix by several different types of specialized mesenchymal cells. Abnormalities of transport of glycoproteins other than lysosomal enzymes or excess of extracellular acid hydrolases may be involved in the pathogenesis.

Parabiotic twin syndrome with topical isocortical disruption and gastroschisis

A case of parabiotic twin pregnancy is described with early fetal co-twin loss and topical isocortical disruption and gastroschisis in the surviving twin. We conclude from this case that early fetal parabiotic twin syndrome (before 16 weeks of gestational age) may cause microgyria and neuronal heterotopia. The cerebral and extracranial findings can be explained as the result of multiple vascular obstructions. Whereas most cases of parabiotic twin syndrome with brain damage involve cystic necrosis, focal hypoplasia with disrupted development in the affected part has been found in the present case. The probable reason in discussed. The roentgenographic analysis of the dead twin fetus is consistent with the period of 13-16 weeks as the likely period in which microgyria and neuronal heterotopia originated in the surviving twin. The present case constitutes one of the rare instances in which neuronal migration disturbance in the human could be dated reliably.