Ultrasound measurement of fetal size in rural Guatemala

Estimating birth weight from observed postnatal weights in a Guatemalan highland community

OBJECTIVE

Low birth weight is one of the leading contributors to global perinatal deaths. Detecting this problem close to birth enables the initiation of early intervention, thus reducing the long-term impact on the fetus. However, in low-and middle-income countries, sometimes newborns are weighted days or months after birth, thus challenging the identification of low birth weight. This study aims to estimate birth weight from observed postnatal weights recorded in a Guatemalan highland community.

APPROACH

With 918 newborns recorded in postpartum visits at a Guatemalan highland community, we fitted traditional infant weight models (Count's and Reeds models). The model that fitted the observed data best was selected based on typical newborn weight patterns reported in the medical literature and previous longitudinal studies. Then, estimated birth weights were determined using the weight gain percentage derived from the fitted weight curve.

MAIN RESULTS

The best model for both genders was the Reeds2 model, with a mean square error of 0.30 kg2 and 0.23 kg2 for male and female newborns, respectively. The fitted weight curves exhibited similar behavior to those reported in the literature, with a maximum weight loss around three to five days after birth, and birth weight recovery, on average, by day ten. Moreover, the estimated birth weight was consistent with the 2015 Guatemalan National Survey, no having a statistically significant difference between the estimated birth weight and the reported survey birth weights (two-sided Wilcoxon rank-sum test; [Formula: see text]).

SIGNIFICANCE

By estimating birth weight at an opportune time, several days after birth, it may be possible to identify low birth weight more accurately, thus providing timely treatment when is required.

Patterns of Fetal Growth Based on Ultrasound Measurement and its Relationship with Small for Gestational Age at Birth in Rural Vietnam

BACKGROUND

Small for gestational age (SGA) is a global health problem. Identifying the timing of fetal growth faltering is critical for developing preventive interventions. We aim to describe patterns of fetal growth and to predict SGA at birth using fetal ultrasound measurements.

METHODS

We studied 1412 pregnant women enrolled in a randomised-controlled trial evaluating maternal micronutrient supplementation in Thai Nguyen province, Vietnam. Ultrasound examinations included biparietal diameter (BPD), head circumference (HC) and abdominal circumference (AC), and femur length (FL). Measures were assessed using the new international fetal growth standards (INTERGROWTH-21st Project). Generalised linear mixed logit regression models were used to examine the association between ultrasound measures and SGA at birth.

RESULTS

Overall fetal growth restriction began in early pregnancy and continued through delivery, but the timing of growth faltering varied by measure: it began by 20 weeks for HC, BPD and AC, earlier as compared to FL growth that started >30 weeks. SGA infants had significantly lower mean fetal growth parameters as early as 14 weeks. Ultrasound measures below the 10th percentile were associated with a two to four times higher risk of SGA at birth compared to fetuses greater than the 50th percentile, with the largest odds ratios for AC (OR 3.9, 95% confidence interval (CI) 2.7, 5.7).

CONCLUSIONS

Fetal growth faltering by ultrasound begins in early gestation among rural Vietnamese populations; these patterns clearly identified those to be born SGA. Efforts to prevent fetal growth faltering must begin early in pregnancy and perhaps even before pregnancy.

Disproportionate early fetal growth predicts postnatal thymic size in humans

Prenatal events can affect neonatal thymus size and adult immune function. The causal insults are unknown, although fetal nutrient restriction is suspected. We used ultrasound at three time points during pregnancy (14, 19 and 30 weeks) to measure the growth of six fetal dimensions in rural Bangladeshi women participating in the Maternal and Infant Nutrition Interventions, Matlab study. Postnatal ultrasound was used to calculate thymic index (TI) at birth, 2, 6 and 12 m. Of the 3267 women recruited, 2861 participated by providing data at least at one fetal biometry and one TI time point. Patterns of fetal growth were summarized using principal components calculated from fetal dimension z-scores. Random effects regression, controlling for infant size and season of measurement were used to relate these patterns to TI. We found that smaller leg length relative to head circumference, characteristic of head-sparing growth restriction, was predictive of lower TI. This association was significant at all time points but strongest in earlier pregnancy. Each standard deviation increase in leg-head proportion was associated with an increase in TI of ∼5%. We conclude that growth patterns typical of poor fetal nutrition are associated with poor thymic development. The greater strength of this association in the first trimester is consistent with a period of vulnerability during the early ontogeny of the thymus and suggests that preventative intervention would need to be given in early pregnancy.

Premature or just small? Training Guatemalan birth attendants to weigh and assess gestational age of newborns: an analysis of outcomes

We describe Guatemalan birth attendants' identification of vulnerable newborns, their evaluation of gestational age and anthropometry, and the validity of the Capurro and New Ballard newborn gestational age assessment methods. We interviewed 49 birth attendants and trained 10 of these women to assess 63 newborns. The Capurro and Ballard methods were correlated (Spearman rho = .75, p < .001) and showed agreement (Bland-Altman plot, difference and bias, -0.33 ± 1.3 weeks). Prematurity was estimated at 27% (Ballard) and 24% (Capurro); low birth weight (LBW) was 30%. Capurro provided a simplified, equivalent estimate of gestational age compared with New Ballard that could be used by birth attendants.

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.

Measurement error for ultrasound fetal biometry performed by paramedics in rural Bangladesh

OBJECTIVES

To document the accuracy and precision of sonographic fetal biometry performed by nine paramedics from rural Bangladesh.

METHODS

Paramedics underwent intensive training (6 weeks) including hands-on practice then underwent a series of standardization exercises. Measurements of each fetus were taken by a highly-trained medical doctor (study supervisor) and the nine paramedics. Crown-rump length (CRL) in fetuses of less than 10 weeks' gestation, and biparietal diameter (BPD), occipitofrontal diameter, head and abdominal circumference (AC) and femur diaphysis length (FL) were measured twice using standard procedures by each paramedic and the medical doctor for each fetus, with at least 20 min between them. Precision was quantified using variance components analysis; the intraobserver error for each of the paramedics was calculated by comparing repeat measurements taken on the same participant, and the measurements obtained by each individual paramedic were also compared with those taken by the others (interobserver error). Accuracy was estimated by comparing the mean of the two measures taken by each paramedic to those taken by the study supervisor using paired t-tests. Bland-Altman plots were used to visually assess the relationship between precision of repeat measurements (intraobserver error) and fetal size.

RESULTS

A total of 180 women, at 7 to 31 weeks' gestation, participated in the study. Intraobserver error of the measurements obtained by the paramedics, expressed as the mean SD, ranged from 0.97 mm for BPD in the first trimester to 7.25 mm for AC in the third trimester, and was larger than the interobserver error (i.e. accounting for a greater proportion of total variance) for most measurements. Interobserver error ranged from 0.00 mm for FL to 3.36 mm for AC, both in the third trimester. For all measurements except CRL, intraobserver error increased with increasing fetal size. The measurements obtained by the paramedics did show some statistically significant differences from those obtained by the study supervisor, but these were relatively small in magnitude.

CONCLUSIONS

Both inter- and intraobserver measurement errors were within the range reported in the literature for studies conducted by technical staff and medical doctors. With intense training, paramedics with no prior exposure to ultrasonography can provide accurate and precise measures of fetal biometry.

Can the growth factors PTHrP, Ihh and VEGF, together regulate the development of a long bone?

Endochondral ossification is the process of differentiation of cartilaginous into osseous tissue. Parathyroid hormone related protein (PTHrP), Indian hedgehog (Ihh) and vascular endothelial growth factor (VEGF), which are synthesized in different zones of the growth plate, were found to have crucial roles in regulating endochondral ossification. The aim of this study was to evaluate whether the three growth factors PTHrP, Ihh and VEGF, together, could regulate longitudinal growth in a normal human, fetal femur. For this purpose, a one-dimensional finite element (FE) model, incorporating growth factor signaling, was developed of the human, distal, femoral growth plate. It included growth factor synthesis in the relevant zones, their transport and degradation and their effects. Simulations ran from initial hypertrophy in the center of the bone until secondary ossification starts at approximately 3.5 months postnatal. For clarity, we emphasize that no mechanical stresses were considered. The FE model showed a stable growth plate in which the bone growth rate was constant and the number of cells per zone oscillated around an equilibrium. Simulations incorporating increased and decreased PTHrP and Ihh synthesis rates resulted, respectively, in more and less cells per zone and in increased and decreased bone growth rates. The FE model correctly reflected the development of a growth plate and the rate of bone growth in the femur. Simulations incorporating increased and decreased PTHrP and Ihh synthesis rates reflected growth plate pathologies and growth plates in PTHrP-/- and Ihh-/- mice. The three growth factors, PTHrP, Ihh and VEGF, could potentially together regulate tissue differentiation.

Changes in maternal weight from the first to second trimester of pregnancy are associated with fetal growth and infant length at birth

BACKGROUND

Despite our knowledge of the negative consequences of stunting during early childhood and the important role that maternal nutritional status plays in the development of intrauterine growth retardation, we do not know the extent to which maternal nutritional status influences the growth in length of the fetus or whether a sensitive period for fetal linear growth exists during gestation.

OBJECTIVE

Our objective was to explore the relation between maternal weight gain during different stages of pregnancy and linear growth of the fetus.

DESIGN

Ultrasound examinations were conducted at 15-24 (x: 17.5) and 28-32 (x: 29.9) wk of gestation in 200 women from 4 rural Guatemalan villages. The associations between maternal weight gain from approximately 10 to 20 and 20 to 30 wk of pregnancy (from the first to the second and from the second to the third trimester, respectively) and fetal linear growth were tested with the use of ordinary least-squares regression.

RESULTS

Maternal weight gain from the first to the second trimester was associated with fetal femur and tibia lengths measured at both means of 17 and 30 wk (P < 0.05) and infant length at birth (P < 0.001). Weight gain from the second to the third trimester of pregnancy did not predict fetal linear growth or infant length at birth.

CONCLUSIONS

Maternal weight change from the first to the second trimester of pregnancy is strongly associated with fetal growth. Mid-gestation may be a sensitive period for fetal linear growth.

Cellular life histories and bow tie biology

Considering the life-long influences of fetal growth biology, it is of interest to further elucidate the nature of the fetal growth process itself. Previous analyses of longitudinal fetal ultrasound data led to the hypothesis that hypoxia signals were important aspects of normal growth biology and directed attention to the place of oxygen as a basic nutrient. From the perspective of the cell, both hypoxia and lack of energy substrate trigger a common adaptive pathway through their effects on ATP availability. Comparative data from animal studies and cell culture provide evidence for an integrated energy/oxygen signaling system that acts redundantly and hierarchically with cellular differentiation programs, providing opportunities for developmental flexibility in response to variable ecologic or environmental challenge. The multinodal and interactive design of the fetal growth process suggests that it follows what has been described as the "bow tie" model of metabolism, with implications for robust and inventive approaches to cell, organ, and whole organism construction.