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

Fetal growth velocity standards from the Fetal Growth Longitudinal Study of the INTERGROWTH-21st Project

BACKGROUND

Human growth is susceptible to damage from insults, particularly during periods of rapid growth. Identifying those periods and the normative limits that are compatible with adequate growth and development are the first key steps toward preventing impaired growth.

OBJECTIVE

This study aimed to construct international fetal growth velocity increment and conditional velocity standards from 14 to 40 weeks' gestation based on the same cohort that contributed to the INTERGROWTH-21st Fetal Growth Standards.

STUDY DESIGN

This study was a prospective, longitudinal study of 4321 low-risk pregnancies from 8 geographically diverse populations in the INTERGROWTH-21st Project with rigorous standardization of all study procedures, equipment, and measurements that were performed by trained ultrasonographers. Gestational age was accurately determined clinically and confirmed by ultrasound measurement of crown-rump length at <14 weeks' gestation. Thereafter, the ultrasonographers, who were masked to the values, measured the fetal head circumference, biparietal diameter, occipitofrontal diameter, abdominal circumference, and femur length in triplicate every 5 weeks (within 1 week either side) using identical ultrasound equipment at each site (4-7 scans per pregnancy). Velocity increments across a range of intervals between measures were modeled using fractional polynomial regression.

RESULTS

Peak velocity was observed at a similar gestational age: 16 and 17 weeks' gestation for head circumference (12.2 mm/wk), and 16 weeks' gestation for abdominal circumference (11.8 mm/wk) and femur length (3.2 mm/wk). However, velocity growth slowed down rapidly for head circumference, biparietal diameter, occipitofrontal diameter, and femur length, with an almost linear reduction toward term that was more marked for femur length. Conversely, abdominal circumference velocity remained relatively steady throughout pregnancy. The change in velocity with gestational age was more evident for head circumference, biparietal diameter, occipitofrontal diameter, and femur length than for abdominal circumference when the change was expressed as a percentage of fetal size at 40 weeks' gestation. We have also shown how to obtain accurate conditional fetal velocity based on our previous methodological work.

CONCLUSION

The fetal skeleton and abdomen have different velocity growth patterns during intrauterine life. Accordingly, we have produced international Fetal Growth Velocity Increment Standards to complement the INTERGROWTH-21st Fetal Growth Standards so as to monitor fetal well-being comprehensively worldwide. Fetal growth velocity curves may be valuable if one wants to study the pathophysiology of fetal growth. We provide an application that can be used easily in clinical practice to evaluate changes in fetal size as conditional velocity for a more refined assessment of fetal growth than is possible at present (https://lxiao5.shinyapps.io/fetal_growth/). The application is freely available with the other INTERGROWTH-21st tools at https://intergrowth21.tghn.org/standards-tools/.

Fetal autopsy parameters standards: biometry, organ weights, and long bone lengths

Fetal and perinatal growth charts and tables are essential for proper interpretation of autopsy anthropometric parameters. These parameters depend on factors that may vary between populations; thus, it is recommended that standards be developed from local target populations to ensure that they are truly representative. In this study, we established standards for a complete set of autopsy fetal parameters, including biometrical measurements, organ weights and long bone lengths, based on autopsy data collected retrospectively from a sample of Portuguese fetuses and neonates. Using a robust statistical regression methodology, to fit mean and standard deviation models, we constructed growth curves for gestational ages between 12 and 42 weeks, which aim to be useful for autopsy examination, particularly in the Portuguese population.

Pathologic diagnosis of achondrogenesis type 2 in a fragmented fetus: case report and evidence-based differential diagnostic approach in the early midtrimester

As a group, lethal genetic skeletal disorders (GSDs) usually result in death within the perinatal period. Because lethal GSDs are often ultrasonographically detectible by early midtrimester, dilation and evacuation (D&E) is the method of choice for elective termination of pregnancy in many institutions. However, because the diagnosis of the lethal GSDs relies heavily upon radiologic examination of fetal remains, reaching an accurate diagnosis in this setting can be challenging. We report an autopsy case of a fetus delivered by D&E at 15 4/7 weeks gestation with radiologic, histologic, and genetic findings compatible with achondrogenesis type 2 and discuss an evidence-based differential diagnostic approach to lethal GSDs terminated by early midtrimester D&E.

Systematic review of methodology used in ultrasound studies aimed at creating charts of fetal size

BACKGROUND

Reliable ultrasound charts are necessary for the prenatal assessment of fetal size, yet there is a wide variation of methodologies for the creation of such charts.

OBJECTIVE

To evaluate the methodological quality of studies of fetal biometry using a set of predefined quality criteria of study design, statistical analysis and reporting methods.

SEARCH STRATEGY

Electronic searches in MEDLINE, EMBASE and CINAHL, and references of retrieved articles.

SELECTION CRITERIA

Observational studies whose primary aim was to create ultrasound size charts for bi-parietal diameter, head circumference, abdominal circumference and femur length in fetuses from singleton pregnancies.

DATA COLLECTION AND ANALYSIS

Studies were scored against a predefined set of independently agreed methodological criteria and an overall quality score was given to each study. Multiple regression analysis between quality scores and study characteristics was performed.

MAIN RESULTS

Eighty-three studies met the inclusion criteria. The highest potential for bias was noted in the following fields: 'Inclusion/exclusion criteria', as none of the studies defined a rigorous set of antenatal or fetal conditions which should be excluded from analysis; 'Ultrasound quality control measures', as no study demonstrated a comprehensive quality assurance strategy; and 'Sample size calculation', which was apparent in six studies only. On multiple regression analysis, there was a positive correlation between quality scores and year of publication: quality has improved with time, yet considerable heterogeneity in study methodology is still observed today.

CONCLUSIONS

There is considerable methodological heterogeneity in studies of fetal biometry. Standardisation of methodologies is necessary in order to make correct interpretations and comparisons between different charts. A checklist of recommended methodologies is proposed.

Fetal peritonitis due to appendiceal rupture: a rare complication of hydrops

A rare complication (appendiceal perforation with meconium peritonitis) was observed in a second trimester fetus affected by nonimmune fetal hydrops due to parvovirus B-19 infection. The complication is not considered specific to this or any other etiology for hydrops, which is highly heterogeneous; rather it is an expression of the fragility and friability of edematous tissues.

Ultrasound estimates of gestational age among perinatally demised: a population-based study

BACKGROUND

Correct estimation of gestational age may improve the quality of obstetric care. We hypothesize that significant differences between traditional and alternative estimates by ultrasound are evident among perinatal deaths.

METHODS

Population-based case series with data linkage between autopsy records and The Medical Birth Registry of Norway, including perinatally demised singletons who were examined by autopsy and post-mortem radiography, having antenatal estimates of gestational age both by the calendar method, as calculated from the first day of the last menstrual period preceding the pregnancy (GAlmp), and by mid-second-trimester ultrasound (GAus), N = 380. The main outcome measure was the distribution of GAlmp and GAus within weight strata.

RESULTS

Mean GAus was 1 week less than mean GAlmp (t-test, p < 0.001). The degree of apparent growth restriction manifest after death, as expressed by both birthweight and by post-mortem radiographic measurements, was fairly well correlated with the degree of downward adjustment of age by ultrasound in the early second trimester (Pearson's correlation, r = - 0.599, p < 0.001). The degree of discrepancy between the ultrasound and the calendar methods was associated both with placenta findings (Kruskal-Wallis test, chi2 = 20.95, p = 0.007) and with the main cause of death (Kruskal-Wallis test, chi2 = 27.65, p = 0.004).

CONCLUSION

Among infants who died perinatally, gestational age seemed to be systematically downward adjusted by mid-second-trimester screening ultrasound, particularly among those who were the most growth retarded at the time of death.

Fetal thoracic measurements in prenatal diagnosis of Jeune syndrome

We describe prenatal sonographic findings in a 34-week fetus with Jeune syndrome or asphyxiating thoracic dystrophy (ATD). The long bones measured were less than third percentile; the thoracic circumference (TC) measured 216 mm (< 2.5th percentile); the abdominal circumference (AC) measured 303.5 mm (50th-75th percentiles) and the rib cage perimeter (RCP) measured was 98 mm. The TC/AC was 0.70 (normal, 0.85) and the RCP/TC was 0.45 (normal, 0.68). Following birth diagnosis of Jeune syndrome was made based on radiographic analysis, which was subsequently confirmed by clinical and postmortem examination. This case highlights the utility of both TC/AC and RCP/TC in diagnosis of ATD and other skeletal dysplasias associated with a small thorax.

Diagnóstico pré-natal

O presente artigo apresenta uma descrição de todos os métodos de diagnóstico pré-natal de anormalidades genéticas e cromossômicas, bem como dos relativos a doenças infecciosas na gravidez. O autor discute as diferenças entre eles, e as novas ferramentas da biologia molecular que são aplicadas nesses diagnósticos. Ao final é feita uma descrição da técnica de diagnóstico pré-implantação e de seu uso in vitro em laboratórios de fertilidade situados a mais de dois mil quilômetros um do outro.

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 growth velocity: kinetic, clinical, and biological aspects

With the aim of determining fetal growth kinetics, prenatal data were analysed which had been longitudinally collected in the framework of a perinatal growth survey. The sample comprised 238 singleton normal pregnancies, selected in Genoa and Turin (between 1987 and 1990), and repeatedly assessed by ultrasound scans (five to nine per pregnancy). Five morphometric traits were considered: BPD (biparietal diameter), OFD (occipitofrontal diameter), HC (head circumference), FDL (femur diaphysis length) and AC (abdomen circumference). Growth rate seemed to increase in the early part of the second trimester, and decrease subsequently: velocity peaks were steeper and earlier for head diameters and circumference (about 18 weeks) than for femur length (20 weeks) and abdomen circumference (22 weeks). Velocity standards were traced using a longitudinal two-stage linear model: this ensures unbiased description of the shape of the growth curve, even when growth kinetics are asynchronous, and efficient estimation of the outer centiles--the most useful for diagnostic purposes.

New autosomal recessive form of amelia

Amelia is a rare, usually sporadic malformation. We report on a family in which three fetuses had amelia of the upper limbs and variable deficiency of the lower limbs. The fetuses also had minor facial anomalies. Recurrence of the condition in sibs of both sexes suggests autosomal recessive inheritance. Recurrent amelia has been documented in only a few families most often associated with a different set of malformations. Possibly, mutations in more than one gene with different modes of transmission can lead to this severe limb deficiency. We speculate that the mutation found in our cases interferes with formation of the apical ectodermal ridge in the upper limbs and results in its premature degeneration in the lower limbs.

The influence of birth order and presentation on intrauterine growth of twins

In order to evaluate the influence of birth order and fetal presentation on antenatal growth of twins we conducted a comparison of prospective measurements of five fetal biometric indices in 50 vertex-vertex and 47 vertex-breech twins. We compared (a) twin A to twin B in both groups; (b) the second and (c) the first twins of both groups. Both groups had similar maternal and neonatal characteristics. The growth curves of the twins were also very similar except for three significant (p < 0.05) deviations: (a) Twin A of the vertex-vertex group, had larger femur length (FL) at 18-19 weeks, abdominal circumference (AC) and estimated fetal weight (EFW) at 29 weeks, and EFW measurements at 36 weeks. (b) Second breech twins, compared to their second vertex cohorts, had significantly smaller biparietal diameter (BPD), head circumference (HC) and FL at 18-19 weeks, BPD and HC at 29 weeks, and EFW at 37 weeks. (c) First twins of the vertex-breech group, as compared to first twins of the vertex-vertex group, had significantly smaller BPD and AC at 18-19 weeks, FL and AC at 21-22 and 29 weeks, FL at 31 weeks, and EFW at 27-28 and 36 weeks' gestation. We concluded that significantly different sonographic fetal indices may be measured at about 20 and 30 weeks' gestation, but not later. An adaptive mechanism attributed to fetal presentation is suggested to explain similar birthweights in spite of these antepartum differences.

Chromosomal and genetic forms of growth failure

This chapter does not deal with single diseases, but gives a general account of chromosomal and genetically caused disturbances of growth; even a complete list and description of the various disorders would, in view of the large number of syndromes involving short stature, exceed its scope. Many chromosomal aberrations are non-viable disturbances of growth that lead to intrauterine amniotic death. Following a brief account of the normal development of the germ cell (gametogenesis, embryogenesis, phenogenesis) to the newborn, the incidence of the various chromosomal disturbances in the different stages of development and the effects on growth are discussed. In the case of chromosomal aberrations, particular attention is paid to the significance of mosaic formation. In addition, the new phenomena of genomic imprinting and uniparental disomy, exemplified by the Prader-Willi syndrome, are dealt with. Uniparental disomy, which was first demonstrated with the aid of molecular genetics, may provide an explanation for the sporadic appearance of many syndromes involving short stature. Many genes and environmental influences are involved in the individual shaping of body size so that a systematic classification of the various syndromes involving short stature is not possible. Finally, attention is drawn to the increased rate of formation of malignant tumours in certain syndromes involving disturbances of growth.

Human growth plate development in the fetal and neonatal period

The development of the normal human upper tibial growth plate was studied at autopsy in 46 stillborns and 79 newborns of 20-41 weeks gestational age. During this time period, the histology of this plate evolves from a highly cellular structure with relatively poor columnar organization and matrix development to the well known structure seen later in postnatal life. The thickness of the growth plate, assessed in the area surrounding the longitudinal tibial axis, decreases continuously from 1.15 mm on the 20th week to 0.6 mm on the 38th week. This decrease results from losses of both matrix and cellular components, mostly of the latter. However, the relative fraction of area occupied by the matrix significantly increased (12%) and matrix area per cell increased 1.5 times over the last half of gestation, indicating a maturation process of the plate towards a more matrix-oriented structure with age. In this maturation process the number of cells per unit area does not change and the average size of the cells appears to decrease. Plate thickness does not decrease further in the final 3 weeks of pregnancy and increases in early neonatal life; this has no apparent influence on the tibial growth rate. In the period under study the relative anatomical participation of the upper tibial growth plate decreases from approximately 4% of the radiographic length of the tibia on the 20th week to less than 1% at term. Present data will provide fetal and neonatal growth plate standards needed to obtain a better understanding of this structure during both normal and abnormal conditions.

The fetal skeleton; ultrasonographic evaluation of the normal growth

A longitudinal study of normal fetal growth is presented as a basis for prenatal diagnosis of skeletal dysplasias. The lengths of fetal limb bones, abdominal circumference, thoracic circumference, head circumference, foot length and orbital diameters were measured in 63 normal fetuses between 12 and 40 weeks of gestation. From these data, ratios were calculated which may have relevance for the prenatal diagnosis of skeletal dysplasias. In addition, rates were calculated for fetal limb growth. From these parameters (absolute measurements, ratios and growth rates), the 10th, 50th and 90th centiles were determined as reference values.

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.