Can growth in dichorionic twins be monitored with individualized growth assessment?

OBJECTIVE

To characterize fetal growth in dichorionic twins using individualized growth assessment (IGA), a method based on individual growth potential estimates.

METHODS

This secondary analysis included 286 fetuses/neonates from 143 dichorionic twin pregnancies that were part of the ESPRiT (Evaluation of Sonographic Predictors of Restricted Growth in Twins) study. The sample was subcategorized according to birth weight into appropriate-for-gestational-age (AGA) (n = 243) and small-for-gestational-age (SGA) (n = 43) cohorts. Serial biometric scans evaluating biparietal diameter, head circumference (HC), abdominal circumference, femur diaphysis length and estimated weight at 2-week intervals were used to evaluate fetal growth, while measurements of birth weight, crown-heel length and HC determined neonatal growth outcome. Six abnormalities (hypoxic ischemic encephalopathy, periventricular leukomalacia, necrotizing enterocolitis, respiratory distress, sepsis and death) constituted the evaluated adverse neonatal outcomes (ANO). IGA was used to: evaluate differences in second-trimester growth velocities between singletons (from a published dataset) and dichorionic twins (138 AGA twins with normal third-trimester growth); describe the degree to which actual third-trimester growth in twins followed expected growth (111 AGA twins, normal fetal growth and neonatal growth outcomes); determine if the fetal growth pathology score 1 (-FGPS1) could detect, quantify and classify twin growth pathology (224 AGA, 42 SGA); and assess the relationship between -FGPS1 and ANO (24 SGA twins with progressive growth restriction confirmed by abnormal neonatal growth outcome).

RESULTS

The differences in second-trimester growth velocity between singletons and twins (means and variances) were small and not statistically significant. Percent deviations from the expected third-trimester size trajectories were within the 95% reference ranges derived from singletons at 95.7% (1677/1752) of timepoints studied. Abnormal growth was detected in 37.9% of AGA twins and 85.7% of SGA twins. Growth restriction was more heterogeneous in AGA twins, while in SGA twins progressive growth restriction was the principal type (66.7%). -FGPS1 patterns previously defined in singletons classified 97.5% of pathological twin cases. In our most severe form of growth restriction (progressive), there were only three (12.5%) ANOs related to growth abnormalities, all in cases with -FGPS1 values more negative than -2.0%. Using these criteria, the frequency of ANO was 33%.

CONCLUSIONS

With respect to growth, dichorionic twins can be considered as two singletons in the same uterus. Normally growing dichorionic twins have the same growth potential as singletons with normal growth outcome. These twins also follow expected third-trimester growth trajectories with the same precision as do singletons. Third-trimester growth pathology can be detected, quantified and classified using -FGPS1 as in singletons. Limited evidence of a relationship between fetal growth abnormalities and adverse neonatal outcome was found. © 2023 International Society of Ultrasound in Obstetrics and Gynecology.

Second-trimester growth velocities in twin and singleton pregnancies

OBJECTIVE

Previous small studies used individualized growth assessment (IGA) to characterize prenatal growth velocities of singletons and twins. We aimed to compare second-trimester growth velocities of individual anatomical parameters between monochorionic diamniotic (MCDA) twins, dichorionic diamniotic (DCDA) twins and singleton fetuses in a larger study.

METHODS

This was a study of a novel cohort of 222 MCDA twins and previously published cohorts of 40 DCDA twins and 118 singletons with serial ultrasound data. Fetal biometric measurements of biparietal diameter, head circumference, abdominal circumference and femur diaphysis length from prenatal ultrasound examinations were used to calculate second-trimester growth velocities using direct calculation or linear regression analysis. Linear fit was assessed based on the coefficient of determination (R² ). Mean growth velocities and variances were compared among the three groups.

RESULTS

The majority of cases underwent three second-trimester ultrasound examinations with fetal biometry available. All fetuses had linear growth, with R² > 99% for all parameters. Only 1-2% of all MCDA and DCDA anatomical parameters had abnormal growth velocity scores outside the 95% reference range for singletons. There were no significant differences in mean growth velocity for any parameter between MCDA twins and singletons. Femur diaphysis length growth velocity was significantly lower in DCDA twins than in both MCDA twins and singletons. There were no other significant differences among the groups.

CONCLUSIONS

Expanding on prior work using IGA, we found that second-trimester growth velocity of the four major anatomical parameters overall was similar between twins and singletons and between MCDA and DCDA twins, supporting the use of singleton-derived growth standards for IGA in twins. Twin growth potential appears to be similar to that of singletons in the second trimester, suggesting that subsequent growth divergence may be due to third-trimester physiological or pathological changes in twin pregnancies. © 2022 International Society of Ultrasound in Obstetrics and Gynecology.

Standards for evaluating neonatal growth outcomes using individualized pathological growth potential realization indices

OBJECTIVE

Provide standards for detecting neonatal growth abnormalities with the average pathological Growth Potential Realization Index (av. pGPRI).

METHODS

Individualized Growth Assessment (IGA) evaluations of 117 neonates with normal growth outcomes were carried out using measurements of WT, HC, AC, ThC and CHL. Growth Potential Realization Index (GPRI) values for each parameter were calculated from predicted and actual birth measurements, the former obtained using Rossavik size models derived from the second-trimester growth potential estimates. Subtraction of either the upper and lower boundaries of GPRI reference ranges from these GPRI measurements gave + pGPRI and - pGPRI measurements. GPRI's within their reference ranges were assigned pGPRI values of zero. Average values for these two types of pGPRI's were calculated for the WT, HC, CHL set (n = 117) and the WT, HC, AC, ThC, CHL set (n = 112).

RESULTS

The 95% reference ranges for the av. +pGPRI's and av. -pGPRI's in the WT, HC, CHL set were 0% to +0.50% and 0% to -0.40%, respectively. In the WT, HC, AC, ThC, CHL set, the comparable results were 0% to +0.50% and 0% to -0.72%.

CONCLUSION

Standards are provided for classifying neonatal growth outcomes with a parameter quantifying growth pathology that was based on individualized growth potentials.

Third-trimester growth diversity in small fetuses classified as appropriate-for-gestational age or small-for-gestational age at birth

OBJECTIVE

We have shown previously that third-trimester growth in small fetuses (estimated fetal weight (EFW) < 10^th percentile) with birth weight (BW) < 10^th percentile is heterogeneous using individualized growth assessment (IGA). We aimed to test our hypothesis that individual growth patterns in small fetuses with BW > 10^th percentile are also variable but in different ways.

METHODS

This was a study of 191 cases with EFW < 10^th percentile and BW > 10^th percentile (appropriate-for-gestational-age (AGA) cohort), derived from the PORTO study. Composite size parameters were used to quantify growth pathology at individual third-trimester timepoints (individual composite prenatal growth assessment score (-icPGAS)). The fetal growth pathology score 1 (-FGPS1), calculated cumulatively from serial -icPGAS values, was used to characterize third-trimester growth patterns. Vascular-system evaluation included umbilical artery (UA) and middle cerebral artery (MCA) Doppler velocimetry. Outcome variables were birth age (preterm/term delivery) and BW (expressed as growth potential realization index for weight (GPRI_WT ) and percentile). The findings from the AGA cohort were compared with those from small fetuses (EFW < 10^th percentile) with BW < 10^th percentile (small-for-gestational-age (SGA) cohort).

RESULTS

The AGA cohort was found to have 134 fetuses (70%) with normal growth pattern and 57 (30%) with growth restriction based on IGA criteria. Seven growth-restriction -FGPS1 patterns were observed, including the previously defined progressive, late, adaptive and recovering types. The recovering type was the most common growth pattern in the AGA cohort (50.9%). About one-third of fetuses without any evidence of growth restriction had significant unexplained abnormalities in the UA (34%) and MCA (31%) and elevated mean GPRI_WT values (113 ± 12.5%). Comparison of the AGA and SGA cohorts indicated a significant difference in the distribution of -FGPS1 growth patterns (P = 0.0001). Compared with the SGA cohort, the AGA cohort had more fetuses with a normal growth pattern (70% vs 38%) and fewer cases with growth restriction (30% vs 62%). While the recovering type was the most common growth-restriction pattern in the AGA cohort (51%), the progressive type was the primary growth-restriction pattern in the SGA cohort (44%). No difference in the incidence of MCA or UA abnormality was found between the SGA and AGA cohorts when comparing subgroups of more than 10 fetuses.

CONCLUSIONS

Both normal-growth and growth-restriction patterns were observed in the AGA cohort using IGA, as seen previously in the SGA cohort. The seven types of growth restriction defined in the SGA cohort were also identified in AGA cases, but their distribution was significantly different. In one-third of cases without evidence of growth pathology in the AGA cohort, Doppler abnormalities in the UA and MCA were seen. This heterogeneity underscores the difficulty of accurate classification of fetal and neonatal growth status using conventional population-based methods. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

Growth patterns and cardiovascular abnormalities in SGA fetuses: 3. Late, adaptive and recovering growth restriction

OBJECTIVE

To characterize abnormal growth processes and their associated cardiovascular abnormalities in SGA fetuses using Individualized Growth Assessment (IGA).

METHODS

This longitudinal investigation utilized a SGA cohort [EFW and BW <10th percentile] derived from the PORTO study. Fetuses categorized by their Fetal Growth Pathology Score [FGPS1] patterns [Pattern 2 {n = 12}, Pattern 3 {n = 11}, Pattern 5 {n = 13}] were evaluated. Growth pathology was measured using the -FGPS1 and the individual composite Prenatal Growth Assessment Score {-icPGAS]. Paired cardiovascular assessments utilized measurements of the Pulsatility Index [umbilical artery {UA}, middle cerebral artery {MCA}, ductus venosus {DV}] and the myocardial performance index [MPI; heart]. Outcome variables were birth age [preterm or, term] and birth weight [small or normal (IGA criteria)].

RESULTS

Pattern 2 was usually characterized by a single, growth abnormality (67% of cases) of variable magnitude that occurred within two weeks of delivery {median onset age: 37.6 weeks}. The incidence of UA abnormalities was low (25%) while those of MCA and DV/MPI were high {60%, 42%}. Most neonates were of normal size (67%) and delivered at term (67%). Pattern 3 had an initial progressive growth restriction phase, followed by constant but abnormally low growth. Growth pathology had an early onset (median age: 31.6 weeks), was moderate but persistently abnormal. The incidences of cardiovascular abnormalities were moderate [30-50%]. Most neonates were abnormally small (80%) but delivered at term (90%). Pattern 5 had an initial progressive phase with an early onset [onset age {median}: 31.6 weeks]. However, this process was arrested and returned toward normal. Growth pathology magnitudes were minor as were the incidences of cardiovascular abnormalities. Neonatal size was usually normal and all fetuses delivered at term.

CONCLUSIONS

Characteristics of SGA Growth Restricted, Patterns 2, 3 and 5 are clearly different from those found in SGA Normal or SGA Growth Restricted Pattern 1 groups. They also differed from one another, indicating that growth restriction can manifest itself in several different ways. Pattern 2 is similar to "late" growth restriction reported previously. Patterns 3 and 5 are novel and have been designated as "adaptive" and "recovering" types of growth restriction.

Growth patterns and cardiovascular abnormalities in SGA fetuses: 2. Normal growth and progressive growth restriction

OBJECTIVES

To characterize growth processes and their associated cardiovascular abnormalities in SGA fetuses with normal growth and progressive growth restriction patterns as defined by Individualized Growth Assessment (IGA).

METHODS

A SGA cohort (EFW and BW < 10th percentile) was derived from the PORTO study that included 47 fetuses with normal growth outcome (SGA Normal) and 34 fetuses with progressive growth restriction (SGA Growth Restricted, Pattern 1). Composite fetal size parameters were used to quantify growth pathology at individual third trimester time points (individual composite Prenatal Growth Assessment Score {icPGAS}) and calculated cumulatively during the third trimester (Fetal Growth Pathology Score 1{FGPS1}). Paired Doppler evaluations of the umbilical artery (UA), middle cerebral artery (MCA), ductus venosus (DV) and myocardial performance index (MPI) were used to detect cardiovascular anomalies. Outcome variables were birth age and birth weight.

RESULTS

Ranking fetuses with respect to the severity of the 3rd trimester growth pathology (-FGPS1) revealed three subgroups in each of these two groups. In SGA Normal, no (51%), minimal (19%) or minor (30%) growth abnormalities were present. Although vascular flow abnormalities occurred without growth abnormalities (UA: 38%; MCA: 35%), they increased with minor growth disturbances (UA: 64%; MCA: 50%). All fetuses delivered at term and in only 7 cases (minor growth abnormalities subgroup) were the neonates abnormally small based on IGA criteria. In SGA Growth Restricted, Pattern 1, the progression of growth restriction was slow (47%), moderate (21%) and rapid (32%). Corresponding median -FGPS1 values were -1.34%, -2.67% and -4.88%, respectively. The median age of onset was 33.6, 29.7 and 29.7 weeks in these three subgroups. UA abnormalities occurred infrequently in the first two subgroups but were found in all cases of rapidly progressing pathology. Similar results were found for the MCA and DV + MPI Doppler parameters (rapid progression: MCA = 50%; DV + MPI = 50%). Premature delivery occurred less frequently with slow progression but was nearly 100% in the moderately and rapidly progressive subgroups.

CONCLUSIONS

Negative FGPS1 growth restriction patterns can be used to classify SGA fetuses. Subgroups, based on ranked -FGPS1 values in both SGA Normal and SGA Growth Restricted Pattern 1 groups had marked differences in cardiovascular abnormalities and neonatal outcomes. The characteristics of these two groups are consistent with small, normally growing fetuses and fetuses with "early" growth restriction, respectively.

Growth patterns and cardiovascular abnormalities in small for gestational age fetuses: 1. Pattern characteristics

BACKGROUND

Fetal growth restriction is being defined as either "early" or "late" depending on age of onset. A recent investigation using individualized assessment has identified five different growth restriction patterns. No previous study has related these patterns to cardiovascular abnormalities.

OBJECTIVES

To determine growth patterns in small fetuses (BW < 10th percentile) using Individualized Growth Assessment (IGA) and to relate cardiovascular abnormalities found with Doppler ultrasound to these patterns.

STUDY DESIGN

A secondary analysis was carried out in 126 fetuses from the PORTO data set having both estimated weights and birth weights below the 10th percentile. Only fetuses with 2nd and 3rd trimester biometry scans appropriate for IGA and cardiovascular assessments were studied. There was one-to-one matching of biometry and Doppler evaluations in the 3rd trimester. Composite growth parameters were used to quantify growth pathology at individual time points (individual composite Prenatal Growth Assessment Score (icPGAS)) and during the 3rd trimester (Fetal Growth Pathology Score {FGPS1}). Normal and growth restriction patterns were identified using plots of FGPS1 values. Doppler measurements were classified as normal or abnormal based on published cross-sectional standards. Outcome variables were birth weight and birth age.

RESULTS

In these SGA cases, 38.2% showed normal fetal growth and 61.8% had growth restriction. In the latter, seven different patterns were observed. Pattern 1 was most common (43.5%), followed by Patterns 5 (16.7%), 2 (15.4%) and 3 (14.1%). The characteristics of Pattern 1 indicated progressive growth restriction while Pattern 5 demonstrated recovery from an initial growth abnormality. Cardiovascular abnormalities were quite variable, with those in the umbilical artery being most frequent in Patterns 1 and 3. Pattern 2 had the highest incidence of middle cerebral artery abnormalities. Umbilical artery abnormalities were similar in the Normal and Pattern 5 groups as were those for the middle cerebral artery. Other cardiovascular abnormalities had low frequencies except in Pattern 2 where the ductus venosus incidence was high. Abnormally small neonates, as identified with IGA, were seen primarily in Patterns 1, 3 and 6 (80-88%). Premature deliveries occurred most frequently in Pattern 1 (56%), followed by Pattern 2 (33%).

CONCLUSIONS

Growth in this SGA Group was very heterogeneous with a significant proportion of these small fetuses growing normally. Growth restriction did not appear to be a single process but was manifest as seven different FGPS1 patterns. Both growth pathology and cardiovascular abnormalities differed among patterns. Further investigation will be required to determine how specific growth abnormalities are related to fetal cardiovascular changes over time.

ISUOG Practice Guidelines: ultrasound assessment of fetal biometry and growth

INTRODUCTION These Guidelines aim to describe appropriate assessment of fetal biometry and diagnosis of fetal growth disorders. These disorders consist mainly of fetal growth restriction (FGR), also referred to as intrauterine growth restriction (IUGR) and often associated with small‐for‐gestational age (SGA), and large‐for‐gestational age (LGA), which may lead to fetal macrosomia; both have been associated with a variety of adverse maternal and perinatal outcomes. Screening for, and adequate management of, fetal growth abnormalities are essential components of antenatal care, and fetal ultrasound plays a key role in assessment of these conditions. The fetal biometric parameters measured most commonly are biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC) and femur diaphysis length (FL). These biometric measurements can be used to estimate fetal weight (EFW) using various different formulae1. It is important to differentiate between the concept of fetal size at a given timepoint and fetal growth, the latter being a dynamic process, the assessment of which requires at least two ultrasound scans separated in time. Maternal history and symptoms, amniotic fluid assessment and Doppler velocimetry can provide additional information that may be used to identify fetuses at risk of adverse pregnancy outcome. Accurate estimation of gestational age is a prerequisite for determining whether fetal size is appropriate‐for‐gestational age (AGA). Except for pregnancies arising from assisted reproductive technology, the date of conception cannot be determined precisely. Clinically, most pregnancies are dated by the last menstrual period, though this may sometimes be uncertain or unreliable. Therefore, dating pregnancies by early ultrasound examination at 8–14 weeks, based on measurement of the fetal crown–rump length (CRL), appears to be the most reliable method to establish gestational age. Once the CRL exceeds 84 mm, HC should be used for pregnancy dating2–4. HC, with or without FL, can be used for estimation of gestational age from the mid‐trimester if a first‐trimester scan is not available and the menstrual history is unreliable. When the expected delivery date has been established by an accurate early scan, subsequent scans should not be used to recalculate the gestational age1. Serial scans can be used to determine if interval growth has been normal. In these Guidelines, we assume that the gestational age is known and has been determined as described above, the pregnancy is singleton and the fetal anatomy is normal. Details of the grades of recommendation used in these Guidelines are given in Appendix 1. Reporting of levels of evidence is not applicable to these Guidelines.

Comparison of fetal size standards obtained with conventional methods and individualized assessment: the effect of adjusting for differences in growth potential

Objective: Detection of fetal growth restriction depends on the biometric standard definitions of normal variability. We examined the impact of correcting for differences in fetal growth potential on the variability of third-trimester size standards.Methods: Size standards, corrected differences in growth potential using Individualized Growth Assessment [IGA], were obtained in 119 pregnancies with normal neonatal growth outcomes. Using the same cohort, a second set of size standards, without these corrections, were determined with mixed modeling [IGA Cross-sectional]. An independent set of size standards, obtained by quantile regression in a population-based sample of 1387 pregnant women [World Health Organization (WHO)], was also evaluated. The anatomical parameters studied included BPD, HC, AC, FDL, THC, HDL, ArmC and EWT whenever possible. The variability measures compared were percent deviation reference range [IGA] or twice the coefficient of variation [IGA Cross-sectional, WHO] at weekly time points between 28 and 38 weeks, menstrual age.Results: All six IGA variabilities were significantly smaller [range: 19-60%] when IGA and IGA-cross-sectional size standards were compared. Similar IGA-WHO comparisons showed that the IGA variabilities for 5 of 6 anatomical parameters were significantly smaller [range: 26-32%; exception: FDL (5.8%)]. Comparisons of cross-sectional size standards gave variable results depending on the anatomical parameter studied.Conclusions: Third-trimester variability measures, based on IGA, were consistently lower than those obtained with conventional cross-sectional methods in normal pregnancies. These results were found when the identical sample was used in both IGA and cross-sectional analyses. Decreased variability can improve the sensitivity of IGA for detecting restricted growth and may be partly responsible for its ability to identify different types of growth abnormalities earlier in pregnancy.

Impact of changes in maternal body composition on birth weight and neonatal fat mass in dichorionic twin pregnancies

Background

Although the impact of gestational weight gain (GWG) on birth weight in twin pregnancies has been demonstrated, the specific components of GWG have not been delineated for twin gestations. Fetal body composition has been shown to be modifiable in singleton gestations based on nutritional intervention strategies and may prove to have similar modifications in twin gestations.

Objective

We aimed to determine the relation of maternal body composition changes to birth weight, birth length, and neonatal fat mass (FM) in dichorionic-diamniotic twin pregnancies.

Design

This is a prospective study of 20 women with twin gestations. Comparisons were made between body composition variables during each trimester and for the entire pregnancy and compared with the outcomes of birth weight, neonatal fat percentage, and birth length.

Results

GWG within or above compared with below the IOM recommendations was associated with higher birth weights (P = 0.03, P = 0.04, respectively), but also with higher postpartum weight retention (P = 0.001). Total maternal protein gain over the pregnancy was positively associated with birth weight (P = 0.03). Changes in maternal fat-free mass (FFM), total body water (TBW), and FM from the first to the third trimester were not associated with either birth weight or neonatal FM percentage. However, maternal FM change from the second to the third trimester was significantly correlated to neonatal FM percentage (P = 0.02). Third trimester GWG and total protein gain were positively correlated with neonatal birth length (P = 0.02 and 0.03, respectively). Maternal FFM over all 3 trimesters showed a positive relation with neonatal birth length (P = 0.01).

Conclusions

Significant increases in maternal protein are associated with greater birth weight and neonatal birth length. Protein accretion, in contrast to TBW and FM gains, may be the most critical component of maternal GWG in dichorionic twin gestations.

Estimated energy requirements increase across pregnancy in healthy women with dichorionic twins

Background

Estimated energy requirement (EER) has not been defined for twin pregnancy. This study was designed to determine the EER of healthy women with dichorionic-diamniotic (DCDA) twin pregnancies.

Objectives

We aimed to estimate energy deposition from changes in maternal body protein and fat; to measure resting energy expenditure (REE), physical activity level (PAL), and total energy expenditure (TEE) throughout pregnancy and postpartum; and to define the EER based on the sum of TEE and energy deposition for twin gestation.

Design

This is a prospective study of 20 women with DCDA twin gestations. Maternal EER, energy deposition, REE, TEE, and PAL were obtained during the first, second, and third trimesters of pregnancy and immediately postpartum. A mixed-effects linear regression model for repeated measures with random intercept was used to test for the effects of BMI groups and time.

Results

Gains in total body protein (mean ± SD: 2.1 ± 0.7 kg) and fat mass (5.9 ± 2.8 kg) resulted in total energy deposition of 67,042 ± 25,586 kcal between 0 and 30-32 weeks of gestation. REE increased 26% from 1392 ± 162 to 1752 ± 172 kcal/d across the 3 trimesters, whereas TEE increased 17% from 2141 ± 283 to 2515 ± 337 kcal/d. Physical activity decreased steadily throughout pregnancy. Reductions in physical activity did not compensate for the rise in REE and energy deposition, thus requiring an increase in dietary energy intake as pregnancy progressed. EER increased 29% from 2257 ± 325 kcal/d in the first trimester to 2941 ± 407 kcal/d in the second trimester, and stayed consistent at 2906 ± 350 kcal/d in the third trimester.

Conclusion

Increased energy intake, on average ∼700 kcal/d in the second and third trimesters when compared with the first trimester, is required to support gestational weight gain and the rise in energy expenditure of DCDA twin pregnancies.

Individualized growth assessment: conceptual framework and practical implementation for the evaluation of fetal growth and neonatal growth outcome

Fetal growth abnormalities can pose significant consequences on perinatal morbidity and mortality of nonanomalous fetuses. The most widely accepted definition of fetal growth restriction is an estimated fetal weight less than the 10th percentile for gestational age according to population-based criteria. However, these criteria do not account for the growth potential of an individual fetus, nor do they effectively separate constitutionally small fetuses from ones that are malnourished. Furthermore, conventional approaches typically evaluate estimated fetal weight at a single time point, rather than using serial scans, to evaluate growth. This article provides a conceptual framework for the individualized growth assessment of a fetus/neonate based on measuring second-trimester growth velocity of fetal size parameters to estimate growth potential. These estimates specify size models that generate individualized third-trimester size trajectories and predict birth characteristics. Comparisons of measured and predicted values are used to separate normally growing fetuses from those with growth abnormalities. This can be accomplished with individual anatomical parameters or sets of parameters. A practical and freely available software (Individualized Growth Assessment Program) has been developed to allow implementation of this approach for clinical and research purposes.

Second trimester growth velocities: assessment of fetal growth potential in SGA singletons

OBJECTIVE

To evaluate the validity of second trimester growth velocities as measures of fetal growth potential in Small-for-Gestational-Age (SGA) singletons.

METHODS

Second trimester growth velocities for biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC) and femur diaphysis length (FDL) were determined by linear regression analysis or direct measurement in 53 SGA singletons with normal growth outcomes (SGA N Group) and 73 with growth restriction (SGA GR) based on a composite fetal growth pathology score (FGPS1). The latter were subdivided into six groups based on their growth restriction pattern (Patterns group). Similar data were available for 118 singletons with normal neonatal growth outcomes (NNGO group). Coefficients of determination (R²) and growth velocities for each anatomical parameter were compared between Patterns subgroups and the SGA N, SGA GR and NNGO groups.

RESULTS

Median R² values in the six Patterns subgroups ranged from 98.2% (Pattern 2, FDL) to 99.9% (Pattern 5, AC). Within each anatomical parameter set, no significant differences were found (Kruskal-Wallis). Patterns subgroup data were pooled to form the SGA GR group for each anatomical parameter. Mean values for the three main groups ranged from 98.4% (SGA N, FDL) to 99.6% (SGA N, HC). No significant differences between groups (ANOVA) were found for any anatomical parameter (ANOVA). Only 1.7-3.8% had R² values <95th%. No significant differences in median second trimester growth velocities among different Patterns subgroups were found for any anatomical parameter. In the SGA N and SGA GR groups, mean BPD and HC values did not differ but were significantly smaller than the NNGO group values. No differences in mean FDL values were seen. With AC, all three means were significantly different, having the following order: NNGO > SGA N > SGA GR. Of all 504 second trimester growth rates, 92.5% were within their respective 95% reference ranges.

CONCLUSION

Growth in the second trimester is linear in fetuses at risk for growth restriction. Except for FDL, growth velocities were lower than those for fetuses with NNGO. Only AC had mean velocities that differed between the SGA N and the SGA GR groups. Since most velocities (92.5%) were within normal reference ranges, they are reasonable measures of growth potential in fetuses at risk for growth restriction.

Third trimester growth restriction patterns: individualized assessment using a fetal growth pathology score

OBJECTIVE

To qualitatively and quantitatively characterize third trimester growth patterns in fetuses/neonates with growth restriction using Individualized Growth Assessment.

METHODS

Serial fetal size measurements from 73 fetuses with proven growth restriction were evaluated using a novel composite parameter, the Fetal Growth Pathology Score (FGPS1). Third trimester FGPS1 measurements plotted against fetal age were examined for patterns. Identified patterns were characterized using the four components of the FGP1 [head circumference (HC), abdominal circumference (AC), femur diaphysis length (FDL), estimated weight (EWT)]. A secondary characterization using age of onset, duration and magnitude of the growth abnormality process was also performed. Frequencies and magnitudes of abnormal values in different FGPS1 patterns were compared.

RESULTS

Five growth restriction patterns were found in 70/73 (95.9%) of the cases, with progressive worsening [Pattern 1 (37.0%)] and abnormal growth identified only at last scan [Pattern 2 (27.4%)] being the most common. These two patterns were usually statistically different from each other and the other three with respect to size parameter abnormalities and abnormal growth process characteristics (MANOVA). Growth abnormalities in all parameters of the FGPS1 contributed to the five abnormality patterns although AC and EWT were most important. The age of onset, duration and magnitude were similar between patterns except for Pattern 2, which had a late onset and a short duration (GLM + contrasts).

CONCLUSIONS

Our study represents the first detailed evaluation of third trimester growth restriction using methods that consider the growth potential of each fetus. Five distinctive and repetitive patterns were found, suggesting that fetal growth restriction evolves in different ways. Further research is needed to determine the relationships of these patterns to physiological/biochemical changes and adverse outcomes associated with growth restriction.

Fetal growth pathology score: a novel ultrasound parameter for individualized assessment of third trimester growth abnormalities

OBJECTIVES

To study fetal growth in pregnancies at risk for growth restriction (GR) using, for the first time, the fetal growth pathology score (FGPS1).

METHODS

A retrospective cohort study of GR was carried out in 184 selected SGA singletons using a novel, composite measure of growth abnormalities termed the FGPS1. Serial fetal biometry was used to establish second trimester Rossavik size models and determine FGPS1 values prior to delivery. FGPS1 data were compared to neonatal growth outcomes assessed using growth potential realization index (GPRI) values (average negative pathological GPRI (av - pGPRI)). Growth at the end of pregnancy was evaluated from differences in negative, individual composite prenatal growth assessment scores (-icPGAS) measured at the last two ultrasound scans. The FGPS1 and av - pGPRI values were used to classify fetal growth and neonatal growth outcomes, respectively, as Normal (N) or Abnormal (A).

RESULTS

The risk of neonatal GR (based on birth weight (BW)) was moderate (MR: between 5th and10th percentiles (n = 113)) or significant (SR:<5th percentile) (n = 71)). Individual pregnancies were grouped into four categories, two representing agreement (N-N (29%), A-A (40%)) and two representing discordance (N-A (11%), A-N (20%)). In the largest and most variable subgroup (A-A,<5%tile, n = 49), there was a statistically significant correlation (0.63, p < .0001) between the FGPS1 and av - pGPRI. In N-A, all 20 cases (100%) had long last-scan-to-delivery intervals (1.9 weeks or greater), suggesting late development of the growth abnormality. For A-N, in approximately equal proportions, GR was improving, progressing or unclassifiable at the end of pregnancy.

CONCLUSIONS

Significant agreement between prenatal and postnatal growth assessments was found using a novel approach for quantifying fetal growth pathology (FGPS1). Discordances appear to be due to lack of appropriate prenatal scans or an inadequate set of neonatal measurements. Evidence for a quantitative relationship between assessment methods was seen in the largest and most variable subgroup. The FGPS1 has the potential for characterizing GR in the third trimester and may provide a means for predicting the severity of corresponding abnormal neonatal growth outcomes.

Growth Patterns of Fetal Lung Volumes in Healthy Fetuses and Fetuses With Isolated Left-Sided Congenital Diaphragmatic Hernia

OBJECTIVES

To evaluate fetal lung growth using 3-dimensional sonography in healthy fetuses and those with congenital diaphragmatic hernia (CDH).

METHODS

Right and total lung volumes were serially evaluated by 3-dimensional sonography in 66 healthy fetuses and 52 fetuses with left-sided CDH between 20 and 37 weeks' menstrual age. Functions fitted to these parameters were compared for 2 groups: (1) healthy versus those with CDH; and (2) fetuses with CHD who survived versus those who died.

RESULTS

Fetal right and total lung volumes as well as fetal observed-to-expected right and total lung volume ratios were significantly lower in fetuses with CDH than healthy fetuses (P< .001) and in those fetuses with CDH who died (P< .001). The observed-to-expected right and total lung volume ratios did not vary with menstrual age in healthy fetuses or in those with CDH (independent of outcome).

CONCLUSIONS

Lung volume rates were lower in fetuses with left-sided CDH compared to healthy fetuses, as well as in fetuses with CDH who died compared to those who survived. The observed-to-expected right and total lung volume ratios were relatively constant throughout menstrual age in fetuses with left-sided CDH, suggesting that the origin of their lung growth abnormalities occurred before 20 weeks and did not progress. The observed-to-expected ratios may be useful in predicting the outcome in fetuses with CDH independent of menstrual age.

Personalized third-trimester fetal growth evaluation: comparisons of individualized growth assessment, percentile line and conditional probability methods

OBJECTIVE

To compare third-trimester size trajectory prediction errors (average transformed percent deviations) for three individualized fetal growth assessment methods.

METHODS

This study utilized longitudinal measurements of nine directly measured size parameters in 118 fetuses with normal neonatal growth outcomes. Expected value (EV) function coefficients and variance components were obtained using two-level random coefficient modeling. Growth models (IGA) or EV coefficients and variance components (PLM and CPM) were used to calculate predicted values at ∼400 third-trimester time points. Percent deviations (%Dev) calculated at these time points using all three methods were expressed as percentages of IGA MA-specific reference ranges [transformed percent deviations (T%Dev)]. Third-trimester T%Dev values were averaged (aT%Dev) for each parameter. Mean ± standard deviation's for sets of aT%Dev values derived from each method (IGA, PLM and CPM) were calculated and compared.

RESULTS

Mean aT%Dev values for nine parameters were: (i) IGA: -4.3 to 5.2% (9/9 not different from zero); (ii) PLM: -32.7 to 25.6% (4/9 not different from zero) and (iii) CPM: -20.4 to 17.4% (5/9 not different from zero). Seven of nine systematic deviations from zero were statistically significant when IGA values were compared to either PLM or CPM values. Variabilities were smaller for IGA when compared to those for PLM or CPM, with (i) 5/9 being statistically significant (IGA versus PLM), (ii) 2/9 being statistically significant (IGA versus CPM) and (iii) 5/9 being statistically significant (PLM versus CPM).

CONCLUSIONS

Significant differences in the agreement between predicted third-trimester size parameters and their measured values were found for the three methods tested. With most parameters, IGA gave smaller mean aT%Dev values and smaller variabilities. The CPM method was better than the PLM approach for most but not all parameters. These results suggest that third-trimester size trajectories are best characterized by IGA in fetuses with normal growth outcomes.

Longitudinal assessment of lung area measurements by two-dimensional ultrasound in fetuses with isolated left-sided congenital diaphragmatic hernia

OBJECTIVE

To evaluate lung growth in healthy fetuses and those with congenital diaphragmatic hernia (CDH) using two-dimensional (2D) ultrasound.

METHODS

Fetal right lung measurements obtained by 2D ultrasound between 19 and 37 weeks' gestation were evaluated longitudinally in 66 healthy fetuses and 52 fetuses with isolated left-sided CDH. Right lung areas were determined by the 'tracing' and 'longest-diameters' methods and, subsequently, lung area-to-head circumference ratios (LHRs) were calculated. Functions fitted to these size parameters with respect to gestational age were evaluated for three sets of group-wise comparisons: (1) healthy vs CDH fetuses; (2) different degrees of severity of CDH; and (3) CDH fetuses that survived vs those that died by 6 months postpartum.

RESULTS

There was a significantly slower increase in right lung areas and LHRs with advancing gestational age in CDH fetuses than in healthy individuals (P < 0.05). Compared to those with milder forms of CDH, lung areas and LHRs of fetuses with more severe forms displayed a smaller increase (P < 0.05) and LHRs of fetuses with severe CDH did not increase during pregnancy (P > 0.05). Individuals who died postpartum did not show any increase in LHR (P > 0.05) throughout gestation.

CONCLUSIONS

The right lung area and LHR, calculated using either the longest-diameters or tracing method, display reduced growth rates during gestation in cases of isolated left-sided CDH as compared with healthy fetuses. The growth curve characteristics of fetal lung areas and LHRs may be useful for predicting neonatal mortality.

Reference ranges for 2-dimensional sonographic lung measurements in healthy fetuses: a longitudinal study

OBJECTIVES

The purpose of this study was to establish reference ranges for 2-dimensional sonographic measurements of fetal lungs from longitudinal data.

METHODS

A total of 214 fetal lung measurements were longitudinally evaluated in 62 healthy fetuses between 20 and 36 weeks' menstrual age. Both right and left lung areas were measured in the heart 4-chamber view using lung area tracing and axis diameter methods. Multilevel modeling was used to evaluate the expected values and variability with respect to menstrual age and to generate reference ranges for the lung area, lung-to-head ratio, quantitative lung index, and observed-to-expected lung-to-head ratio for both lungs.

RESULTS

The expected values varied with menstrual age for all parameters. Variance was menstrual age dependent for all parameters except the longest diameter area measurements and their lung-to-head ratios.

CONCLUSIONS

Models are presented for expected 2-dimensional sonographic lung size parameters and their variance as a function of menstrual age. These data have been used to generate age-specific reference ranges for both measurements and indices.

The effect of maternal body mass index on fetal growth: use of individualized growth assessment and two-level linear modeling

PURPOSE

To determine the effect of maternal body mass index on fetal growth using individualized growth assessment and two-level linear modeling.

METHODS

A retrospective review of biometry in the second and third trimesters from 246 normal, term singleton fetuses was performed. Four to eight biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), and femur diaphysis length (FDL) measurements per fetus were available and used to determine second-trimester growth rates. Expected third-trimester size trajectories were generated from these data and Percent Deviations [%Dev = ((observed - expected)/expected) × 100] were calculated. Two-level linear modeling was used to determine %Dev slopes and the effect of body mass index (BMI) on these slopes. Relationships between individual second- and third-trimester slopes and BMI were evaluated using linear regression.

RESULTS

Linear regression analysis of second-trimester growth indicated no significant relationships between the fetal growth rate and the BMI in the second trimester [R(2) (adj): 0.0% to 1.0% except AC in one subgroup (5.6%)]. Regression analysis did not indicate a significant relationship (adj R(2) : 0%-0.2%) between BMI and third-trimester %Dev slopes for any anatomic parameter. Two-level statistical modeling showed no effect of BMI on BPD, AC, or FDL growth and only a moderate effect on the HC growth in the third trimester.

CONCLUSIONS

Our findings indicate that the maternal BMI does not have an effect on fetal growth in either the second or the third trimester as determined with individualized growth assessment.

Fetal growth cessation in late pregnancy: its impact on predicted size parameters used to classify small for gestational age neonates

OBJECTIVE

To evaluate the impact of late 3rd trimester fetal growth cessation on anatomical birth characteristic predictions used in classifying SGA neonates.

METHODS

A prospective longitudinal study was performed in 119 pregnancies with normal neonatal growth outcomes. Seven biometric parameters were measured at 3-4 weeks intervals using 3D ultrasonography. Rossavik size models were determined to predict birth characteristics at different ages. Percent Differences (% Diff) were calculated from predicted and measured birth characteristics. Growth Cessation Ages (GCA) were identified when no systematic change in % Diff values occurred after specified prediction ages. Systematic and random prediction errors were compared using different assumptions about the GCA. Predicted and measured size parameters were used to determine six new Growth Potential Realization Index (GPRI) reference ranges. Five were used to sub-classify 34 SGA neonates (weight < 10th percentile) based on the number of abnormal GPRI values.

RESULTS

Growth cessation ages were 38 weeks for HC, AC, mid-thigh circumference, estimated weight and mid-arm circumference. Crown-heel length GCA was 38.5 weeks. At GCA, birth characteristics had prediction errors that varied from 0.08 ± 3.4% to 15.7 ± 9.1% and zero % Diff slopes after 38 weeks. Assuming growth to delivery gave increased systematic and random prediction errors as well as positive % Diff slopes after 38 weeks, MA. Seventeen of the SGA neonates had 0 or 1 abnormal GPRI values [Subgroup 1] and 17 others had 2 or more abnormal values [Subgroup 2]. In Subgroup 1, 4/85 (4.7%) of GPRI's were abnormal while in Subgroup 2, 43/85 (50.6%) were abnormal. Use of only one type of GPRI for SGA subclassification resulted in substantial false negative and some false positive rates when compared to subclassification based on all five GPRI values.

CONCLUSIONS

Growth cessation occurred at approximately 38 weeks for all six birth characteristics studied. SGA neonates can be separated into normal and growth restricted subgroups based on the frequency of abnormal GPRI values (GPRI Profile Classification).

A modified prenatal growth assessment score for the evaluation of fetal growth in the third trimester using single and composite biometric parameters

OBJECTIVE

To define modified Prenatal Growth Assessment Scores (mPGAS) for single and composite biometric parameters and determine their reference ranges in normal fetuses.

METHODS

Nine anatomical parameters (ap) were measured and the weight estimated (EWTa, EWTb) in a longitudinal study of 119 fetuses with normal neonatal growth outcomes. Expected third trimester size trajectories, obtained from second trimester Rossavik size models, were used in calculating Percent Deviations (% Dev's) and their age-specific reference ranges in each fetus. The components of individual % Dev's values outside their reference ranges, designated +iapPGAS, -iapPGAS, were averaged to give +apPGAS and -apPGAS values for the 3rd trimester. The +iapPGAS and -iapPGAS values for different combinations of ap (c1a (HC, AC, FDL, ThC, EWTa), c1b (HC, AC, FDL, ThC, EWTb), c2 (ThC, ArmC, AVol, TVol), c3 (HC, AC, FDL, EWTa)) were then averaged to give +icPGAS and -icPGAS values at different time points or at the end of the third trimester (+cPGAS, -cPGAS). Values for iapPGAS, ic1bPGAS, and ic2PGAS were compared to their respective apPGAS or cPGAS reference ranges.

RESULTS

All mPGAS values had one 95% range boundary at 0.0%. Upper boundaries of 1D +apPGAS values ranged from 0.0% (HC) to +0.49% (ThC) and were +0.06%, +2.3% and +1.8% for EWT, AVol and TVol, respectively. Comparable values for -apPGAS were 0.0% (BPD, FDL, HDL), to -0.58% (ArmC), -0.13% (EWT), -0.8% (AVol), and 0.0% (TVol). The +cPGAS, 95% reference range upper boundaries varied from +0.36% (c1b) to +0.89% (c2). Comparable values for -cPGAS lower boundaries were -0.17% (c1b) to -0.43% (c2).

CONCLUSIONS

The original PGAS concept has now been extended to individual biometric parameters and their combinations. With the standards provided, mPGAS values can now be tested to see if detection of different types of third trimester growth problems is improved.

Individualized fetal growth assessment: critical evaluation of key concepts in the specification of third trimester size trajectories

OBJECTIVES

To characterize second and third trimester fetal growth using Individualized Growth Assessment methods in a larger cohort of fetuses with normal neonatal growth outcomes.

METHODS

A prospective longitudinal study of 119 pregnancies was performed from 18 weeks, MA, to delivery. Measurements of several 1D and 3D fetal size parameters were obtained from 3D volume data sets at 3-4 week intervals. Regression analyses were used to determine Start Points (SP) and Rossavik model (P = c {t} (k + st)) coefficients c. k and s for each parameter in each fetus. Second trimester growth velocity reference ranges were determined and size model specification functions re-established, the latter used to generate individual size models. Actual measurements were compared to predicted third trimester size trajectories using Percent Deviations. New age-specific reference ranges for the Percent Deviations of each parameter were defined using 2-level statistical modeling.

RESULTS

Rossavik models fit the data for all parameters very well (R(2): 99%), with SP's and k values similar to those found in much smaller cohorts. The c* values were strongly related to the second trimester slope (R(2): 97%), as was predicted s* to estimated c* (R(2): 54--95%). Rossavik models predicted third trimester growth with systematic errors close to 0%; random errors (95% range) ranged between 5.7 and 10.9% and 20.0 and 24.3% for 1D and 3D parameters, respectively.

CONCLUSIONS

IGA procedures for evaluating second and third trimester growth are now established based on a larger cohort (4-6 fold larger). New, more rigorously defined, age-specific standards for the evaluation of third trimester size deviations are now available for nine anatomical parameters and a weight estimation procedure that incorporates a soft tissue parameter (fractional thigh volume). These results provide a means for more reliably assessing fetal growth on an individualized basis, thus minimizing the effect of biological differences in growth.

The relationship of newborn adiposity to fetal growth outcome based on birth weight or the modified neonatal growth assessment score

OBJECTIVES

(1) Develop reference ranges of neonatal adiposity using air displacement plethysmography. (2) Use new reference ranges for neonatal adiposity to compare two different methods of evaluating neonatal nutritional status.

METHODS

Three hundred and twenty-four normal neonates (35-41 weeks post-menstrual age) had body fat (%BF) and total fat mass (FM, g) measured using air displacement plethysmography shortly after delivery. Results were stratified for 92 of these neonates with corresponding fetal biometry using two methods for classifying nutritional status: (1) population-based weight percentiles; and (2) a modified neonatal growth assessment score (m(3)NGAS(51)).

RESULTS

At the 50th percentile, %BF varied from 7.7% (35 weeks) to 11.8% (41 weeks), while the corresponding 50th percentiles for total FM were 186-436 g. Among the subset of 92 neonates, no significant differences in adiposity were found between small for gestational age (SGA), appropriate for gestational age (AGA), and large for gestational age (LGA) groups using population-based weight standards. Classification of the same neonates using m(3)NGAS(51) showed significant differences in mean %BF between corresponding groups.

CONCLUSIONS

Population-based weight criteria for neonatal nutritional status can lead to misclassifications on the basis of adiposity. A neonatal growth assessment score, that considers the growth potential of several anatomic parameters, appears to more effectively classify under- and over-nourished newborns.

New fetal weight estimation models using fractional limb volume

OBJECTIVES

The main goal of this study was to determine the accuracy and precision of new fetal weight estimation models, based on fractional limb volume and conventional two-dimensional (2D) sonographic measurements during the second and third trimesters of pregnancy.

METHODS

A prospective cross-sectional study of 271 fetuses was performed using three-dimensional ultrasonography to extract standard measurements-biparietal diameter (BPD), abdominal circumference (AC) and femoral diaphysis length (FDL)-plus fractional arm volume (AVol) and fractional thigh volume (TVol) within 4 days of delivery. Weighted multiple linear regression analysis was used to develop 'modified Hadlock' models and new models using transformed predictors that included soft tissue parameters for estimating birth weight. Estimated and observed birth weights were compared using mean percent difference (systematic weight estimation error) and the SD of the percent differences (random weight estimation error). The proportion of newborns with estimated birth weight within 5 or 10% of actual birth weight were compared using McNemar's test.

RESULTS

Birth weights in the study group ranged from 235 to 5790 g, with equal proportions of male and female infants. Six new fetal weight estimation models were compared with the results for modified Hadlock models with sample-specific coefficients. All the new models were very accurate, with mean percent differences that were not significantly different from zero. Model 3 (which used the natural logarithms of BPD, AC and AVol) and Model 6 (which used the natural logarithms of BPD, AC and TVol) provided the most precise weight estimations (random error = 6.6% of actual birth weight) as compared with 8.5% for the best original Hadlock model and 7.6% for a modified Hadlock model using sample-specific coefficients. Model 5 (which used the natural logarithms of AC and TVol) classified an additional 9.1% and 8.3% of the fetuses within 5% and 10% of actual birth weight and Model 6 classified an additional 7.3% and 4.1% of infants within 5% and 10% of actual birth weight.

CONCLUSION

The precision of fetal weight estimation can be improved by adding fractional limb volume measurements to conventional 2D biometry. New models that consider fractional limb volume may offer novel insight into the contribution of soft tissue development to weight estimation.

Fetal growth parameters and birth weight: their relationship to neonatal body composition

OBJECTIVES

The main goal was to investigate the relationship between prenatal sonographic parameters and birth weight in predicting neonatal body composition.

METHODS

Standard fetal biometry and soft tissue parameters were assessed prospectively in third-trimester pregnancies using three-dimensional ultrasonography. Growth parameters included biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), mid-thigh circumference and femoral diaphysis length (FDL). Soft tissue parameters included fractional arm volume (AVol) and fractional thigh volume (TVol) that were derived from 50% of the humeral or femoral diaphysis lengths, respectively. Percentage of neonatal body fat (%BF) was determined within 48 h of delivery using a pediatric air displacement plethysmography system based on principles of whole-body densitometry. Correlation and stepwise multiple linear regression analyses were performed with potential prenatal predictors and %BF as the outcome variable.

RESULTS

Eighty-seven neonates were studied with a mean +/- SD %BF of 10.6 +/- 4.6%. TVol had the greatest correlation with newborn %BF of all single-parameter models. This parameter alone explained 46.1% of the variability in %BF and the best stepwise multiple linear regression model was: %BF = 0.129 (TVol) - 1.03933 (P < 0.001). Birth weight similarly explained 44.7% of the variation in %BF. AC and estimated fetal weight (EFW) accounted for only 24.8% and 30.4% of the variance in %BF, respectively. Skeletal growth parameters, such as FDL (14.2%), HC (7.9%) and BPD (4.0%), contributed the least towards explaining the variance in %BF.

CONCLUSIONS

During the late third trimester of pregnancy %BF is most highly correlated with TVol. Similar to actual birth weight, this soft tissue parameter accounts for a significant improvement in explaining the variation in neonatal %BF compared with fetal AC or EFW alone.

Fractional limb volume--a soft tissue parameter of fetal body composition: validation, technical considerations and normal ranges during pregnancy

OBJECTIVES

The main goals were to provide normal reference ranges for fractional limb volume as a new index of generalized fetal nutritional status, to evaluate the reproducibility of fractional fetal limb volume measurements during the second and third trimesters of pregnancy, and to demonstrate technical considerations for this technique.

METHODS

This was a prospective, cross-sectional study of gravid women during mid to late pregnancy. Fractional limb volumes were based on either 50% of humeral or femoral diaphysis length. Each partial volume was subdivided into five equidistant slices that were centered along the mid-arm or mid-thigh. Slices were traced manually to obtain fractional arm (AVol) or fractional thigh (TVol) volume. Reproducibility studies were performed, using Bland-Altman plots, to assess blinded interobserver and intraobserver measurement bias and agreement. Selected images were chosen to demonstrate technical factors for the acquisition and analysis of these parameters. Reference charts were established to describe normal ranges for AVol and TVol.

RESULTS

Three hundred and eighty-seven subjects were scanned to include 380 AVol (range, 1.1-68.3 mL) and 378 TVol (range 2.0-163.2 mL) measurements between 18.0 and 42.1 weeks' menstrual age. No gender differences were found in these soft tissue measurements (AVol, P = 0.90; TVol, P = 0.91; Mann-Whitney test). Intraobserver mean bias +/- SD and 95% limits of agreement (LOA) for fractional limb volumes were: 2.2 +/- 4.2% (95% LOA, - 6.0 to 10.5%) for AVol and 2.0 +/- 4.2% (95% LOA, - 6.3 to 10.3%) for TVol. Interobserver bias and agreement were - 1.9 +/- 4.9% (95% LOA, - 11.6 to 7.8%) for AVol and - 2.0 +/- 5.4% (95% LOA, - 12.5 to 8.6%) for TVol. Technical factors were related to image optimization, transducer pressure, fetal movement, soft tissue compression and amniotic fluid volume.

CONCLUSIONS

Fractional limb volume assessment may improve the detection and monitoring of malnourished fetuses because this soft tissue parameter can be obtained quickly and reproducibly during mid to late pregnancy. Careful attention should be placed on technical factors that can potentially affect optimal acquisition and analysis of these volume measurements.

Individualized growth assessment of fetal thigh circumference using three-dimensional ultrasonography

OBJECTIVES

To develop individualized growth assessment (IGA) standards for upper (ThC(u)) and middle (ThC(m)) fetal thigh circumferences using three-dimensional ultrasonography.

METHODS

A prospective, longitudinal sonographic study of 30 fetuses was performed beginning at 18 weeks' menstrual age. Second-trimester sonographic parameters were measured from three-dimensional volume data to establish IGA standards. Normal infant growth outcomes were confirmed using modified Neonatal Growth Assessment Scores (m(3)NGAS(51)). ThC(u) and ThC(m) were studied in more detail. Rossavik growth model specification procedures, based on the slopes of the second-trimester growth curves, were developed for both ThC(u) and ThC(m). Third-trimester growth trajectories and birth measurements were subsequently predicted for these parameters. Percentage deviations during the third trimester and percentage differences at actual birth age were used to compare observed and predicted measurements. The 95% ranges for Growth Potential Realization Index (GPRI) values for both types of thigh circumference were determined. Values for m(3)NGAS(51) using GPRI(ThC(u)), GPRI(ThC(m)) and GPRI(ThC(o)) (original method) were compared.

RESULTS

The 30 newborns had no postnatal evidence of abnormal growth. Two examiners demonstrated a satisfactory measurement bias of mean +/- SD 2.1 +/- 3.6 (95% limits of agreement,-4.9 to 9.1)% for ThC(m) and 3.3 +/- 4.1 (95% limits of agreement,-4.8 to 11.4)% for ThC(u). Rossavik functions fitted parameter trajectories well, with mean R(2) values of 99.5 +/- 0.4% for ThC(u) and 99.6 +/- 0.3% for ThC(m). By fixing coefficients k at their mean values, their respective fits did not change, and the variabilities of coefficients c and s were significantly reduced. For ThC(u), coefficient c was significantly related to the second-trimester slope (R(2)=98.6%), as was s to c(R(2)=91.0%). For ThC(m), coefficient c was significantly related to the second-trimester slope (R(2)=98.6%), as was s to c(R(2)=85.6%). Third-trimester growth trajectories, derived from second-trimester slopes for individual fetuses, had third-trimester deviations of 0.07 +/- 3.7% for ThC(u) and-0.04 +/- 3.7% for ThC(m). Percentage differences at birth age were 16.8 +/- 10.2% for ThC(u) and 8.9 +/- 9.5% for ThC(m). With correction for systematic overestimations, the mean GPRI values were 103.7 (95% range, 90-121)% for ThC(u) and 101.6 (95% range, 88-118)% for ThC(m). Corresponding mean +/- SD m(3)NGAS(51) values, using GPRI(ThC(u)), GPRI(ThC(m)) and GPRI(ThC(o)), were 203 +/- 11%, 201 +/- 10% and 200 +/- 9%, respectively.

CONCLUSIONS

Fetal thigh circumference can be measured reliably and evaluated using standard IGA methods. Both ThC(u) and ThC(m) give similar results in the third trimester but neonatal thigh circumference predictions are improved by using ThC(m). Corresponding GPRI(ThC(m)) values are closer to the ideal value of 100% and can be used in m(3)NGAS(51) calculations for assessment of neonatal growth outcome.

Guidelines for the use and interpretation of assays for monitoring autophagy in higher eukaryotes

Research in autophagy continues to accelerate,(1) and as a result many new scientists are entering the field. Accordingly, it is important to establish a standard set of criteria for monitoring macroautophagy in different organisms. Recent reviews have described the range of assays that have been used for this purpose.(2,3) There are many useful and convenient methods that can be used to monitor macroautophagy in yeast, but relatively few in other model systems, and there is much confusion regarding acceptable methods to measure macroautophagy in higher eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers of autophagosomes versus those that measure flux through the autophagy pathway; thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from fully functional autophagy that includes delivery to, and degradation within, lysosomes (in most higher eukaryotes) or the vacuole (in plants and fungi). Here, we present a set of guidelines for the selection and interpretation of the methods that can be used by investigators who are attempting to examine macroautophagy and related processes, as well as by reviewers who need to provide realistic and reasonable critiques of papers that investigate these processes. This set of guidelines is not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to verify an autophagic response.

Quantitative assessment of gestational sac shape: the gestational sac shape score

OBJECTIVE

To develop a quantitative method for characterizing gestational sac shape.

METHODS

Twenty first-trimester gestational sacs in normal pregnancies were studied with three-dimensional (3D) ultrasonography. The 3D coordinates of surface-point sets were obtained for each sac using 30-, 15- and six-slice sampling. Cubic spline interpolation was used with the 15- and six-slice surface-point samples to generate coordinates for those 30-slice surface points not measured. Interpolated and measured values, the latter from the 30-slice sample, were compared and the percent error calculated. Cubic spline interpolation was used to determine the coordinates of a standard surface-point sample (3660) for each sac in each slice sample. These coordinate data were used to give each sac a standard configuration by moving its center of gravity to the origin, aligning its inertial axes along the coordinate axes and converting its volume to 1.0 mL. In this form, a volume shape descriptor could be generated for each sac that was then transformed into a vector containing only shape information. The 20 shape vectors of each slice sample were subjected to principal components analysis, and principal component scores (PCSs) calculated. The first four PCSs were used to define a gestational sac shape score (GSSS-30, GSSS-15 or GSSS-6) for each sac in a given slice sample. The characteristics of each set of GSSSs were determined and those for the GSSS-15 and GSSS-6 were compared with the GSSS-30 characteristics.

RESULTS

Cubic spline interpolations were very accurate in most cases, with means close to 0%, and approximately 95% of the errors being less than 10%. GSSS-30 accounted for 67.6% of the shape variance, had a mean of zero and an SD of 1.1, was normally distributed and was not related to menstrual age (R=-0.16, P=0.51). GSSS-15 and GSSS-6 had essentially the same characteristics. No significant differences between individual GSSS-30 values and those for GSSS-15 or GSSS-6 were found, indicating the absence of a slice sample effect.

CONCLUSION

Using sophisticated mathematical methods, the gestational sac shape, initially represented by the 3D coordinates of 3660 surface points, was converted to a single number, the GSSS. This score had the appropriate properties for quantitatively characterizing normal, first-trimester gestational sac shapes. As it can be obtained from as few as six slices, it should be useful in many clinical situations. This novel approach has the potential for providing quantitative shape information about a variety of biological shapes and how they change over time.

Quantitative and morphological assessment of early gestational sacs using three-dimensional ultrasonography

OBJECTIVE

Our main objective was to determine the value of three-dimensional ultrasonography (3DUS) and Virtual Organ Computer-aided AnaLysis (VOCAL) in the evaluation of gestational sac volume and morphology during early pregnancy.

METHODS

Twenty-eight normal early pregnancies were scanned approximately every 2 weeks using transabdominal (TAS) and transvaginal (TVS) sonography. The VOCAL technique was used to create computerized surface models to classify gestational sac shapes as discoid or ellipsoid. Serial sac volume changes were analyzed using repeated measures ANOVA. Bland-Altman plots determined examiner bias and limits of agreement (LOA) for sac volume measurements. Gestational sac volumes were compared between the two-dimensional (2D) ellipsoid and VOCAL techniques. Differences between volume measurements were tested using the two-tailed paired t-test with statistical significance at the P < 0.05 level.

RESULTS

Each subject was examined at a mean +/- SD menstrual age of 7.9 +/- 0.6 weeks (Scan 1), 9.9 +/- 0.6 weeks (Scan 2), and 11.9 +/- 0.6 weeks (Scan 3). Sac volumes significantly increased over time from 22 +/- 11 mL at Scan 1, to 57 +/- 21 mL at Scan 2 and 116 +/- 35 mL at Scan 3 (P < 0.001). Predominant sac shapes were classified as ellipsoid (76.2%) or discoid (23.8%). Additional descriptors included: concave (60.7%), irregular (53.6%), or smooth (7.1%), with 19% of the overall group having more than one additional shape attribute. Clinically acceptable volume measurement bias and agreement were found for the following comparisons: (1) TAS versus TVS; (2) interobserver volume measurements; and (3) intraobserver volume measurements. The VOCAL technique yielded slightly greater sac volumes (64 +/- 45.4 mL) when compared to the 2D ellipsoid model (48.6 +/- 36.8 mL) (28.9 +/- 24.3% (95% limit of agreement range, - 18.7 to 76.5%), P < 0.001).

CONCLUSIONS

Reproducible sac volume measurements can be obtained using VOCAL with either TAS or TVS. Early gestational sacs variably appear as discoid or ellipsoid structures with a concave indentation from the placenta. Sac volumes can be underestimated if an ellipsoid shape is assumed. Morphological and quantitative analysis of the gestational sac may provide baseline parameters for studying patients at risk for early pregnancy failure.

Correlation between middle cerebral artery peak systolic velocity and fetal hemoglobin after 2 previous intrauterine transfusions

OBJECTIVE

The middle cerebral artery peak systolic velocity (MCA-PSV) has been successfully used for timing the first 2 transfusions in fetuses at risk for anemia because of maternal red cell alloimmunization. The objective of this study was to assess whether the correlation between the MCA-PSV and fetal hemoglobin is maintained in fetuses that had undergone 2 previous intrauterine transfusions.

STUDY DESIGN

Doppler measurement of MCA-PSV was performed before cordocentesis in 39 fetuses. The timing of the third transfusion was based on traditional criteria. The values of MCA-PSV and hemoglobin were expressed as multiples of the median (MoM). Anemia was defined as mild (hemoglobin <0.84 MoM for a given gestational age, moderate (hemoglobin <0.65 MoM), and severe (hemoglobin <0.55 MoM). Regression analysis was used to assess the correlation between the MCA-PSV MoM and fetal hemoglobin MoM.

RESULTS

Gestational age at Doppler study ranged from 22 to 35 weeks. Six fetuses (15%) had normal hemoglobin concentration; 21 (53%) had mild anemia; 7 (20%) had moderate anemia; and 5 (12%) had severe anemia. There was a linear correlation between fetal hemoglobin (y) and the MCA-PSV (x): y = 1.185 - 0.341x.

CONCLUSION

Previously, concerns have been expressed about the accuracy of Doppler prediction of anemia after previous transfusions. Our data suggest that there is a good correlation between the MCA-PSV and fetal hemoglobin in fetuses that have undergone 2 previous transfusions. Our findings expand the clinical situation in which Doppler can be used to monitor red cell alloimmunized pregnancies.

The fetal arm: individualized growth assessment in normal pregnancies

OBJECTIVE

The goals were to introduce fractional arm volume (AVol) as a new soft tissue parameter of fetal growth assessment and to develop individualized growth standards, based on Rossavik models, for AVol, midarm circumference (ArmC), and humeral diaphysis length (HDL).

METHODS

A prospective longitudinal study of 22 fetuses was conducted using 2- and 3-dimensional sonography. Three new growth parameters (HDL, ArmC, and AVol) were used to establish individualized standards for arm growth with the use of Rossavik functions [P=c(t)k (+) s(t), where P is the anatomic parameter; c, k, and s are model coefficients; and t is the time variable]. Second-trimester models were specified from the linear slopes of growth curves before approximately 28.0 menstrual weeks. For a given fetus, normal third-trimester trajectories were predicted for each parameter. Observed and predicted measurements were compared by percent deviations.

RESULTS

Rossavik functions fit all parameter trajectories extremely well (R(2)=95.7%-99.4%). By fixing coefficients k at their mean values, their respective fits did not change, and the variabilities of both coefficients c and s were reduced. Coefficient c was also significantly related to second-trimester slope, as was s to c, for all 3 parameters (R(2)=97.7%-98.7%; P<.0001). Mean percent deviations between observed and predicted third-trimester HDL, ArmC, and AVol measurements were -0.1% +/- 2.9%, 0.5% +/- 4.6%, and 0.4% +/- 8.5%, respectively.

CONCLUSIONS

Individualized growth assessment, using HDL and ArmC, can accurately predict normal arm growth during the third trimester of pregnancy. AVol may also allow earlier detection and improved monitoring of soft tissue abnormalities that can occur in fetuses with growth disturbances.

Individualized growth assessment of fetal soft tissue using fractional thigh volume

OBJECTIVES

The main goals of this study were to introduce fractional thigh volume (TVol) as a new soft tissue parameter for fetal growth evaluation, define its relationship to menstrual age, and develop individualized fetal growth standards based on Rossavik growth models.

METHODS

A prospective, longitudinal study of 22 fetuses was conducted with conventional biometry and TVol measurements by three-dimensional ultrasonography. Infant growth outcomes were determined from modified neonatal growth assessment scores. Rossavik functions (P = c(t)k+s(t)) were used to fit complete datasets to examine relationships between TVol and model coefficients. Second-trimester models were subsequently specified from the linear slopes of growth curves before 28.0 menstrual weeks with each fetus acting as its own control. Third-trimester trajectories and birth measurements were predicted for standard growth parameters and TVol. Observed and predicted measurements were compared using percent deviations and growth potential realization index values. Four additional infants, with serial prenatal scans and postnatal evidence of intrauterine growth restriction (IUGR), were also evaluated.

RESULTS

All 22 fetuses had no evidence of growth abnormalities after delivery. Accelerated soft tissue deposition occurred in the fetal thigh by 28 menstrual weeks. A mean TVol start point of 9.0 +/- 1.4 menstrual weeks was consistent with embryological studies of thigh development. Rossavik functions fitted all TVol trajectories well (mean R2 = 0.998 +/- 0.002). By fixing the coefficient k at its mean value (2.976), the fit did not change and the variabilities of coefficients c and s were reduced. The mean percent deviation between observed and predicted third-trimester TVol measurements was -0.048 +/- 7.5%. Relatively early pathological deviations were observed for TVol in all four fetuses with IUGR; in these cases the abdominal circumference was abnormal in only one fetus and thigh circumference in none.

CONCLUSIONS

Individualized growth assessment can be used to accurately predict TVol during the third trimester of pregnancy and at birth. Expected growth trajectories, from second-trimester data, do not rely on population-based standards because each fetus serves as its own control. This new parameter may allow earlier detection and improved monitoring of fetal soft tissue abnormalities such as IUGR.

Individualized growth assessment: evaluation of growth using each fetus as its own control

In Individualized Growth Assessment, each fetus serves as its own control. Rossavik growth models [P = c[t](k + s[t])] for the 5 anatomical parameters of the Prenatal Growth Profile are specified from 2nd trimester measurements obtained from a given fetus. These growth models are used to determine expected 3rd trimester growth trajectories and to predict birth characteristics. Actual measurements obtained in the 3rd trimester and at birth are compared to expected measurements by calculation of Percent Deviation and Growth Potential Realization Index values, parameters proportional to the difference between measured and expected average growth rates in the 3rd trimester. Prenatal Growth Assessment Scores and modified Neonatal Growth Assessment Scores, calculated from Percent Deviation and Growth Potential Realization Index values for the 5 anatomical parameters, respectively, can be used to detect growth abnormalities manifesting themselves differently in different individuals. Individualized Growth Assessment methods have effectively identified growth abnormalities in fetuses and neonates except in prenatal cases where only a change in soft tissue has occurred.

Identification of Macrosomic, Normal and Intrauterine Growth Retarded Neonates Using the Modified Neonatal Growth Assessment Score

OBJECTIVE

Separation of Macrosomic, normal and intrauterine growth retarded (IUGR) neonates using the modified Neonatal Growth Assessment Score (NGAS).

METHODS

A sample of 23 neonates with evidence of growth acceleration and 74 neonates classified as normal or IUGR in a previous study was used in this investigation. The prenatal growth of all neonates had been studied longitudinally with ultrasound. From the data collected, Rossavik models describing the growth trajectories of head circumference (HC), abdominal circumference (AC), thigh circumference (ThC), femur diaphysis length, head cube (A) and abdominal cube (B) were specified. These models were used to predict birth weight (WT), crown-heel length (CHL), HC, AC and ThC at birth. Actual birth measurements of WT, CHL, HC, AC and ThC were evaluated using age-specific normal size curves and compared to predicted measurements by means of the growth potential realization index (GPRI). GPRI values were evaluated by comparison to previously established normal ranges and used to calculate Neonatal Growth Assessment Scores (NGAS(5)). NGAS(5) values, together with assessments of anatomical measurements and GPRI values, were used to establish macrosomic, normal and IUGR groups. Principal components analysis was applied to the sets of GPRI values available for each neonate to provide a principal component score for separating macrosomic and normal neonates (m(2)NGAS(51)) or one to separate macrosomic, normal and IUGR neonates (m(3)NGAS(51)) using linear discriminant analysis. The groups identified by these multivariate methods were compared to the original classification and their characteristics evaluated.

RESULTS

The m(2)NGAS(51) and a boundary value of 207.5% separated macrosomic and normal neonates with an accuracy of 97.3%. The m(3)NGAS(51) and boundary values of 210.0 and 182.5% separated macrosomic, normal and IUGR neonates with an accuracy of 96.9%. No single GPRI value or anatomical measurement could achieve these levels of accuracy. All normal infants were AGA but only 45.5% of the IUGR group were SGA and only 60.9% of the macrosomic group were LGA. Thirteen different types of IUGR and eleven different types of macrosomia were identified based on GPRI values.

CONCLUSION

The modified NGAS accurately separates macrosomic, normal and IUGR neonates although growth abnormalities are expressed in different ways in different individuals.

An endothelial nitric oxide synthase gene polymorphism is associated with preeclampsia

OBJECTIVE

We sought to test the hypothesis that a polymorphism of the endothelial nitric oxide synthase gene (NOS3) is associated with preeclampsia.

METHODS

We collected and performed polymerase chain reaction (PCR) on genomic DNA from pregnant patients with and without preeclampsia. Patient history and clinical course were evaluated.

MAIN OUTCOME MEASURE(S)

Frequency of the intron 4 polymorphism of NOS3 (designated allele A) among patients with preeclampsia compared with controls. Clinical features of patients with preeclampsia and the A allele compared with those patients with preeclampsia who did not have the A allele.

RESULTS

The frequency of the A allele was 0.10 among controls versus 0.39 among patients with preeclampsia (p < 0.01). The odds ratio of developing preeclampsia when at least one A allele was present was 6.5 [95% confidence interval (CI): 2.1-19.7]. After adjusting for ethnic variation, the odds ratio increased to 7.2 (95% CI: 2.0-25.5). Among patients with preeclampsia, systolic blood pressure at the time of admission was higher for patients with at least one A allele compared with patients homozygous for the B allele (168 versus 156 mm Hg; p = 0.03), independent of gestational age (p = 0.01).

CONCLUSION

These data provide evidence for an association between NOS3 and preeclampsia. In defined ethnic groups, this NOS3 may offer predictive information regarding the subsequent development of preeclampsia and its clinical course.

Birth weight prediction by three-dimensional ultrasonography: fractional limb volume

OBJECTIVE

To introduce fractional limb volume as a new ultrasonographic parameter, validate reliability of fractional limb volume measurements, develop new birth weight prediction models, and examine their practical utility for estimating fetal weight during late pregnancy.

METHODS

Healthy late-third-trimester fetuses were prospectively scanned by two- and three-dimensional ultrasonography within 4 days of delivery. Volume data sets were subsequently used to extract several standard ultrasonographic measurements. Fractional limb volumes of the upper arm and thigh were based on 50% of diaphyseal bone length. Intraclass correlation was used to analyze interobserver and intraobserver reliability of fractional limb volume measurements. Several weight prediction models were developed by linear regression analysis. New prediction models were prospectively compared with the Hadlock formula in 30 healthy late-third-trimester fetuses.

RESULTS

One hundred fetuses were scanned at a mean +/- SD menstrual age of 39.2 +/- 1.2 weeks. Intraclass correlation indicated a significant degree of interobserver and intraobserver reliability for fractional thigh volume. Fractional thigh volume (r = 0.86), fractional upper arm volume (r = 0.83), abdominal circumference (r = 0.83), and midthigh circumference (r = 0.82) were most highly correlated with birth weight. The best prediction model (abdominal circumference and fractional thigh volume) gave weight estimates that deviated from actual birth weight by -0.025% +/- 7.8%. For late-third-trimester fetuses, the Hadlock model yielded errors of 9.0% +/- 9.0%. Prospective testing confirmed superior performance of the new prediction model, which gave accuracy of 2.3% +/- 6.6% (Hadlock method, 8.4% +/- 8.7%). It correctly predicted 20 of 30 birth weights to within 5% of actual weight. By comparison, the Hadlock model predicted only 6 of 30 birth weights to within 5% of actual weight.

CONCLUSIONS

A new birth weight prediction model, based on fractional thigh volume and abdominal circumference, is reliable during the late third trimester. It provides a means for including soft tissue evaluation for birth weight prediction. This rapid technique avoids technical limitations that currently hinder the practical implementation of three-dimensional ultrasonography for estimating birth weight.

Perinatal morbidity and mortality rates in severe twin-twin transfusion syndrome: results of the International Amnioreduction Registry

OBJECTIVE

Serial aggressive amnioreduction is the most widely used therapy for pregnancies that are complicated by twin-twin transfusion syndrome. Survival rates reported with this therapy are 33% to 83%, the wide range attributable to the small number of patients in these case series. Similarly, data on morbidity in survivors are imprecise. We instituted the international twin-twin transfusion syndrome registry to determine the perinatal survival and morbidity rates and the factors that influence perinatal outcome in patients with twin-twin transfusion syndrome who were treated with serial aggressive amnioreduction from 1990 to 1998.

STUDY DESIGN

A total of 223 sets of twins who were diagnosed with twin-twin transfusion syndrome before 28 weeks' gestation from 20 fetal medicine referral centers were analyzed, with follow-up data until 4 weeks after birth.

RESULTS

Three hundred forty-six twins (78%; 182 recipients and 164 donors) were born alive. Two hundred sixty-six twins (60%; 144 recipients and 122 donors) were alive 4 weeks after birth. Both fetuses survived to 4 weeks in 108 pregnancies (48.4%), whereas, at least 1 fetus survived in 158 pregnancies (70.8%). The interval between the last amnioreduction and delivery ranged from zero to 138 days (median, 17.5 days). In the infants who survived to 4 weeks after birth, abnormalities on neonatal cranial scan were diagnosed in 24% of recipients and in 25% of donors. Logistic regression analysis indicated that the survival rate was significantly related to gestational age at diagnosis, presence of end-diastolic blood flow in the umbilical artery velocity waveforms, presence of hydrops, mean volume of amniotic fluid removed per week, larger birth weight, and gestational age at delivery. The hemoglobin level difference at birth was the only significant parameter to predict abnormal cranial ultrasonography in newborns.

CONCLUSION

These data document perinatal survival and neonatal morbidity rates in severe twin-twin transfusion syndrome that were treated by serial aggressive amnioreduction. Outcome was influenced by several perinatal risk factors, which may be used to counsel patients before and during therapy.