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

Association between fetal growth restriction and stillbirth in twin compared with singleton pregnancies

OBJECTIVES

Twin pregnancies are at higher risk of stillbirth compared to singletons. Fetal growth restriction (FGR) is a major cause of perinatal mortality, but its impact on twins vs singletons remains unclear. The primary objective of this study was to investigate the association of FGR and small-for-gestational age (SGA) with stillbirth in twin compared with singleton pregnancies. A secondary objective was to assess these associations stratified by gestational age at delivery. Furthermore, we aimed to compare the associations of FGR and SGA with stillbirth in twin pregnancies using twin-specific vs singleton birth-weight charts, stratified by chorionicity.

METHODS

This was a retrospective cross-sectional study of pregnancies receiving obstetric care and giving birth between 1999 and 2022 at St George's Hospital, London, UK. The exclusion criteria included triplet and higher-order pregnancies, those resulting in miscarriage or live birth at ≤ 23 + 6 weeks, termination of pregnancy and missing data regarding birth weight or gestational age at birth. Birth-weight data were collected and FGR and SGA were defined as birth weight <5th and <10th centiles, respectively. While standard logistic regression was used for singleton pregnancies, the association of FGR and SGA with stillbirth in twin pregnancies was investigated using mixed-effects logistic regression models. For twin pregnancies, intercepts were allowed to vary for twin pairs to account for intertwin dependency. Analyses were stratified by gestational age at delivery and chorionicity. Statistical significance was set at P ≤ 0.001.

RESULTS

The study included 95 342 singleton and 3576 twin pregnancies. There were 494 (0.52%) stillbirths in singleton and 41 (1.15%) stillbirths in twin pregnancies (17 dichorionic and 24 monochorionic). SGA and FGR were associated significantly with stillbirth in singleton pregnancies across all gestational ages at delivery: the odds ratios (ORs) for SGA and FGR were 2.36 ((95% CI, 1.78-3.13), P < 0.001) and 2.67 ((95% CI, 2.02-3.55), P < 0.001), respectively, for delivery before 32 weeks; 2.70 ((95% CI, 1.71-4.31), P < 0.001) and 2.82 ((95% CI, 1.78-4.47), P < 0.001), respectively, for delivery between 32 and 36 weeks; and 3.85 ((95% CI, 2.83-5.21), P < 0.001) and 4.43 ((95% CI, 3.16-6.12), P < 0.001), respectively, for delivery after 36 weeks. In twin pregnancies, when stratified by gestational age at delivery, both SGA and FGR determined by twin-specific birth-weight charts were associated with increased odds of stillbirth for those delivered before 32 weeks (SGA: OR, 3.87 (95% CI, 1.56-9.50), P = 0.003 and FGR: OR, 5.26 (95% CI, 2.11-13.01), P = 0.001), those delivered between 32 and 36 weeks (SGA: OR, 6.67 (95% CI, 2.11-20.41), P = 0.001 and FGR: OR, 9.54 (95% CI, 3.01-29.40), P < 0.001) and those delivered beyond 36 weeks (SGA: OR, 12.68 (95% CI, 2.47-58.15), P = 0.001 and FGR: OR, 23.84 (95% CI, 4.62-110.25), P < 0.001). However, the association of stillbirth with SGA and FGR in twin pregnancies was non-significant when diagnosis was based on singleton charts (before 32 weeks: SGA, P = 0.014 and FGR, P = 0.005; 32-36 weeks: SGA, P = 0.036 and FGR, P = 0.008; after 36 weeks: SGA, P = 0.080 and FGR, P = 0.063).

CONCLUSION

Our study demonstrates that SGA and, especially, FGR are associated significantly with an increased risk of stillbirth across all gestational ages in singleton pregnancies, and in twin pregnancies when twin-specific birth-weight charts are used. © 2024 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Ultrasound parameters of arteries and heart in normal fetuses

BACKGROUND

Currently, no normal ultrasound data of the fetuses during the 20-40 gestation have been obtained for references of fetal growth and development. If such ultrasound data existed for prenatal diagnosis of possible diseases and abnormalities, neonates would be able to get timely treatment immediately after birth. This study was thus performed to obtain ultrasound parameters of normal fetuses during the 20-40 week gestation and the distribution of ultrasound parameters with the gestational age for references of detecting potential fetal diseases and abnormalities.

METHODS

Normal fetuses without any abnormalities were enrolled, and the ultrasound parameters of the general biology, arteries, and aorta were measured and analyzed.

RESULTS

417 normal fetuses were enrolled. A significant (P < 0.05) negative correlation with the gestational age was detected in the peak systolic velocity/peak diastolic velocity (S/D), pulsatility index (PI) and resistance index (RI) of the umbilical artery (UA). A relatively stable relationship with the gestational age was detected in the fetal weight%, S/D, PI and RI of the middle cerebral artery (MCA), peak systolic velocity (PSV) and velocity time integral (VTI) of the intra-abdominal UA, fetal heart to chest ratio, mitral valve (MV)- and tricuspid valve (TV)-E/A peak flow velocity, aortic isthmic Z-score and displacement, distance between the brachiocephalic artery-left common carotid artery (BA-LCCA) and LCCA-left subclavian artery (LSA), Z-score of aorta, ascending aorta (AAO), pulmonary artery (PA), main pulmonary artery (MPA), and descending aorta (DAO). A significant (P < 0.05) positive correlation with the gestational age was detected in the fetal biological data, MCA PSV and VTI, free-UA PSV and VTI and cardio-thoracic ratio, cardiac parameters, ductus arteriosus (DA) and isthmus diameter, aortic parameters, PA and MPA diameter, MPA PSV and VTI, isthmus flow volume and velocity and PA flow volume, DA and BA parameters, and LCCA and LSA parameters (flow volume, PSV, and VTI).

CONCLUSION

A certain correlation and distribution trend is detected in the ultrasound parameters of normal fetuses, and the ratios among different parameters remain relative stable. These findings can be used for determination of abnormal growth of the fetuses in prenatal ultrasound scan.

Fetal Growth Velocity-A Breakthrough in Intrauterine Growth Assessment?

The pursuit of assessing fetal well-being in obstetrical practice remains a central tenet, propelling ongoing endeavors to explore innovative markers and diagnostic methodologies aimed at prognosing potential perinatal adversities. Deviations from standard patterns of intrauterine growth, whether exhibiting excessive or insufficient trajectories, stand as pivotal indices hinting at underlying pathophysiological processes or heightened concurrent medical conditions. Initiatives like the Delphi consensus and the INTERGROWTH-21st project strive to refine diagnostic criteria and establish international standards for fetal growth assessment. This article aims to present the current knowledge regarding the assessment of abnormal growth, including novel methods such as growth velocity. Integrating fetal growth velocity assessment into perinatal care protocols holds promise in enhancing diagnostic precision. Growth velocity, involving changes in fetal size over a given period, offers insights into distinguishing between constitutional and pathological growth abnormalities. Various methodologies and models have been proposed to evaluate growth velocity, with notable advancements in understanding fetal growth patterns across different trimesters. It is believed that accelerated and reduced growth velocity may be a sensible parameter in the detection of fetal growth restriction (FGR), small-for-gestational-age (SGA) fetuses, large-for-gestational-age (LGA) fetuses and macrosomic fetuses as well as appropriate-for-gestational age (AGA) fetuses that encounter problems with growth continuation. Recent studies found that changes in growth velocity reflect the risk of adverse perinatal outcomes (APOs). Future directions in fetal health research aim to elucidate the long-term consequences of abnormal fetal growth velocity on neurodevelopmental outcomes, highlighting the critical role of early assessment and intervention.

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.

Fetal growth restriction and small for gestational age as predictors of neonatal morbidity: which growth nomogram to use?

BACKGROUND

Fetal growth nomograms were developed to screen for fetal growth restriction and guide clinical care to improve perinatal outcomes; however, existing literature remains inconclusive regarding which nomogram is the gold standard.

OBJECTIVE

This study aimed to compare the ability of 4 commonly used nomograms (Hadlock, International Fetal and Newborn Growth Consortium for the 21st Century, Eunice Kennedy Shriver National Institute of Child Health and Human Development-unified standard, and World Health Organization fetal growth charts) and 1 institution-specific reference to predict small for gestational age and poor neonatal outcomes.

STUDY DESIGN

This was a retrospective cohort study of all nonanomalous singleton pregnancies undergoing ultrasound at ≥20 weeks of gestation between 2013 and 2020 and delivering at a single academic center. Using random selection methods, the study sample was restricted to 1 pregnancy per patient and 1 ultrasound per pregnancy completed at ≥22 weeks of gestation. Fetal biometry data were used to calculate estimated fetal weight and percentiles according to the aforementioned 5 nomograms. Maternal and neonatal data were extracted from electronic medical records. Logistic regression was used to estimate the association between estimated fetal weight of <10th and <3rd percentiles compared with estimated fetal weight of 10th to 90th percentile as the reference group for small for gestational age and the neonatal composite outcomes (perinatal mortality, hypoxic-ischemic encephalopathy or seizures, respiratory morbidity, intraventricular hemorrhage, necrotizing enterocolitis, hyperbilirubinemia or hypoglycemia requiring neonatal intensive care unit admission, and retinopathy of prematurity). Receiver operating characteristic curve contrast estimation (primary analysis) and test characteristics were calculated for all nomograms and the prediction of small for gestational age and the neonatal composite outcomes. We restricted the sample to ultrasounds performed within 28 days of delivery; moreover, similar analyses were completed to assess the prediction of small for gestational age and neonatal composite outcomes.

RESULTS

Among 10,045 participants, the proportion of fetuses classified as <10th percentile varied across nomograms from 4.9% to 9.7%. Fetuses with an estimated fetal weight of <10th percentile had an increased risk of small for gestational age (odds ratio, 9.9 [95% confidence interval, 8.5-11.5] to 12.8 [95% confidence interval, 10.9-15.0]). In addition, the estimated fetal weight of <10th and <3rd percentile was associated with increased risk of the neonatal composite outcome (odds ratio, 2.4 [95% confidence interval, 2.0-2.8] to 3.5 [95% confidence interval, 2.9-4.3] and 5.7 [95% confidence interval, 4.5-7.2] to 8.8 [95% confidence interval, 6.6-11.8], respectively). The prediction of small for gestational age with an estimated fetal weight of <10th percentile had a positive likelihood ratio of 6.3 to 8.5 and an area under the curve of 0.62 to 0.67. Similarly, the prediction of the neonatal composite outcome with an estimated fetal weight of <10th percentile had a positive likelihood ratio of 2.1 to 3.1 and an area under the curve of 0.55 to 0.57. When analyses were restricted to ultrasound within 4 weeks of delivery, among fetuses with an estimated fetal weight of <10th percentile, the risk of small for gestational age increased across all nomograms (odds ratio, 16.7 [95% confidence interval, 12.6-22.3] to 25.1 [95% confidence interval, 17.0-37.0]), and prediction improved (positive likelihood ratio, 8.3-15.0; area under the curve, 0.69-0.75). Similarly, the risk of neonatal composite outcome increased (odds ratio, 3.2 [95% confidence interval, 2.4-4.2] to 5.2 [95% confidence interval, 3.8-7.2]), and prediction marginally improved (positive likelihood ratio, 2.4-4.1; area under the curve, 0.60-0.62). Importantly, the risk of both being small for gestational age and having the neonatal composite outcome further increased (odds ratio, 21.4 [95% confidence interval, 13.6-33.6] to 28.7 (95% confidence interval, 18.6-44.3]), and the prediction of concurrent small for gestational age and neonatal composite outcome greatly improved (positive likelihood ratio, 6.0-10.0; area under the curve, 0.80-0.83).

CONCLUSION

In this large cohort, Hadlock, recent fetal growth nomograms, and a local population-derived fetal growth reference performed comparably in the prediction of small for gestational age and neonatal composite outcomes.

Stillbirth risk and smallness for gestational age according to Hadlock, INTERGROWTH-21st, WHO, and GROW fetal weight standards: analysis by maternal ethnicity and body mass index

BACKGROUND

Appropriate growth charts are essential for fetal surveillance, to confirm that growth is proceeding normally and to identify pregnancies that are at risk. Many stillbirths are avoidable through antenatal detection of the small-for-gestational-age fetus. In the absence of an international consensus on which growth chart to use, it is essential that clinical practice reflects outcome-based evidence.

OBJECTIVE

This study investigated the performance of 4 internationally used fetal weight standards and their ability to identify stillbirth risk in different ethnic and maternal size groups of a heterogeneous population.

STUDY DESIGN

We analyzed routinely collected maternity data from more than 2.2 million pregnancies. Three population-based fetal weight standards (Hadlock, Intergrowth-21st, and World Health Organization) were compared with the customized GROW standard that was adjusted for maternal height, weight, parity, and ethnic origin. Small-for-gestational-age birthweight and stillbirth risk were determined for the 2 largest ethnic groups in our population (British European and South Asian), in 5 body mass index categories, and in 4 maternal size groups with normal body mass index (18.5-25.0 kg/m2). The differences in trend between stillbirth and small-for-gestational-age rates were assessed using the Clogg z test, and differences between stillbirths and body mass index groups were assessed using the chi-square trend test.

RESULTS

Stillbirth rates (per 1000) were higher in South Asian pregnancies (5.51) than British-European pregnancies (3.89) (P<.01) and increased in both groups with increasing body mass index (P<.01). Small-for-gestational-age rates were 2 to 3-fold higher for South Asian babies than British European babies according to the population-average standards (Hadlock: 26.2% vs 12.2%; Intergrowth-21st: 12.1% vs 4.9%; World Health Organization: 32.2% vs 16.0%) but were similar by the customized GROW standard (14.0% vs 13.6%). Despite the wide variation, each standard's small-for-gestation-age cases had increased stillbirth risk compared with non-small-for-gestation-age cases, with the magnitude of risk inversely proportional to the rate of cases defined as small for gestational age. All standards had similar stillbirth risk when the small-for-gestation-age rate was fixed at 10% by varying their respective thresholds for defining small for gestational age. When analyzed across body mass index subgroups, the small-for-gestation-age rate according to the GROW standard increased with increasing stillbirth rate, whereas small-for-gestation-age rates according to Hadlock, Intergrowth-21st, and World Health Organization fetal weight standards declined with increasing body mass index, showing a difference in trend (P<.01) to stillbirth rates across body mass index groups. In the normal body mass index subgroup, stillbirth rates showed little variation across maternal size groups; this trend was followed by GROW-based small-for-gestation-age rates, whereas small-for-gestation-age rates defined by each population-average standard declined with increasing maternal size.

CONCLUSION

Comparisons between population-average and customized fetal growth charts require examination of how well each standard identifies pregnancies at risk of adverse outcomes within subgroups of any heterogeneous population. In both ethnic groups studied, increasing maternal body mass index was accompanied by increasing stillbirth risk, and this trend was reflected in more pregnancies being identified as small for gestational age only by the customized standard. In contrast, small-for-gestation-age rates fell according to each population-average standard, thereby hiding the increased stillbirth risk associated with high maternal body mass index.

Dynamic growth changes in fetal growth restriction using serial ultrasonographic biometry and umbilical artery doppler: The multicenter PORTO study

OBJECTIVE

To describe the growth dynamics of fetuses with initial fetal growth restriction (FGR) later outgrowing the 10th centile for estimated fetal weight with respect to perinatal outcomes and maternal factors.

METHODS

A multicenter prospective study recruited 1116 patients for ultrasound surveillance between 2010 and 2012. All pregnancies were growth-restricted singleton gestations between 24 + 0 and 36 + 0 weeks. Biometry and Doppler analysis were carried out, and delivery and adverse perinatal outcomes were recorded.

RESULTS

A total of 193 (17%) fetuses outgrew their diagnosis of initial FGR (surpassed the 10th centile) on their last sonogram before delivery. These fetuses were termed "growers," to compare with the true FGR group. The mothers of "growers" were less likely to be smokers (14% vs 25%, P = 0.0001) or affected by hypertensive pregnancy complications (5.2% vs 15%, P = 0.001). Of the growers, 49 (25%) had an abnormal umbilical artery Doppler; however, in most cases (33/49, 67%), this was a single episode of raised umbilical artery pulsatility index, which subsequently normalized.

CONCLUSION

There were dynamic growth changes in FGR fetuses, with 17% outgrowing their original diagnosis. Positive growth spurts more commonly occurred in healthy mothers. Once a fetus had outgrown the 10th centile, antenatal surveillance could be decreased.

Reduced fetal growth velocity and weight loss are associated with adverse perinatal outcome in fetuses at risk of growth restriction

BACKGROUND

Although fetal size is associated with adverse perinatal outcome, the relationship between fetal growth velocity and adverse perinatal outcome is unclear.

OBJECTIVE

This study aimed to evaluate the relationship between fetal growth velocity and signs of cerebral blood flow redistribution, and their association with birthweight and adverse perinatal outcome.

STUDY DESIGN

This study was a secondary analysis of the TRUFFLE-2 multicenter observational prospective feasibility study of fetuses at risk of fetal growth restriction between 32⁺⁰ and 36⁺⁶ weeks of gestation (n=856), evaluated by ultrasound biometry and umbilical and middle cerebral artery Doppler. Individual fetal growth velocity was calculated from the difference of birthweight and estimated fetal weight at 3, 2, and 1 week before delivery, and by linear regression of all available estimated fetal weight measurements. Fetal estimated weight and birthweight were expressed as absolute value and as multiple of the median for statistical calculation. The coefficients of the individual linear regression of estimated fetal weight measurements (growth velocity; g/wk) were plotted against the last umbilical-cerebral ratio with subclassification for perinatal outcome. The association of these measurements with adverse perinatal outcome was assessed. The adverse perinatal outcome was a composite of abnormal condition at birth or major neonatal morbidity.

RESULTS

Adverse perinatal outcome was more frequent among fetuses whose antenatal growth was <100 g/wk, irrespective of signs of cerebral blood flow redistribution. Infants with birthweight <0.65 multiple of the median were enrolled earlier, had the lowest fetal growth velocity, higher umbilical-cerebral ratio, and were more likely to have adverse perinatal outcome. A decreasing fetal growth velocity was observed in 163 (19%) women in whom the estimated fetal weight multiple of the median regression coefficient was <-0.025, and who had higher umbilical-cerebral ratio values and more frequent adverse perinatal outcome; 67 (41%; 8% of total group) of these women had negative growth velocity. Estimated fetal weight and umbilical-cerebral ratio at admission and fetal growth velocity combined by logistic regression had a higher association with adverse perinatal outcome than any of those parameters separately (relative risk, 3.3; 95% confidence interval, 2.3-4.8).

CONCLUSION

In fetuses at risk of late preterm fetal growth restriction, reduced growth velocity is associated with an increased risk of adverse perinatal outcome, irrespective of signs of cerebral blood flow redistribution. Some fetuses showed negative growth velocity, suggesting catabolic metabolism.

Fetal growth restriction and stillbirth: Biomarkers for identifying at risk fetuses

Fetal growth restriction (FGR) is a major cause of stillbirth, prematurity and impaired neurodevelopment. Its etiology is multifactorial, but many cases are related to impaired placental development and dysfunction, with reduced nutrient and oxygen supply. The fetus has a remarkable ability to respond to hypoxic challenges and mounts protective adaptations to match growth to reduced nutrient availability. However, with progressive placental dysfunction, chronic hypoxia may progress to a level where fetus can no longer adapt, or there may be superimposed acute hypoxic events. Improving detection and effective monitoring of progression is critical for the management of complicated pregnancies to balance the risk of worsening fetal oxygen deprivation in utero, against the consequences of iatrogenic preterm birth. Current surveillance modalities include frequent fetal Doppler ultrasound, and fetal heart rate monitoring. However, nearly half of FGR cases are not detected in utero, and conventional surveillance does not prevent a high proportion of stillbirths. We review diagnostic challenges and limitations in current screening and monitoring practices and discuss potential ways to better identify FGR, and, critically, to identify the “tipping point” when a chronically hypoxic fetus is at risk of progressive acidosis and stillbirth.

Fetal growth restriction with abnormal individual biometric parameters at second trimester ultrasound is associated with small for gestational age neonate at delivery

OBJECTIVES

To determine if early-onset fetal growth restriction with abnormal individual biometric parameters, defined as head circumference, abdominal circumference and femur length less than the 10th percentile, is associated with adverse neonatal outcomes compared to fetal growth restriction with normal biometric parameters.

STUDY DESIGN

Retrospective cohort study including women diagnosed with fetal growth restriction between 16 and 24 weeks gestation who delivered a singleton, non-anomalous neonate at Mount Sinai Hospital from 2013 to 2019. The primary outcome was rate of small for gestational age neonate at delivery. Maternal, obstetric and neonatal outcomes were compared using multivariable regression analysis.

RESULTS

Patients diagnosed with fetal growth restriction with abnormal biometric parameters were more likely to be nulliparous, diagnosed with severe growth restriction and to receive antenatal corticosteroids than those with normal biometric parameters. The rate of small for gestational age neonate at delivery was higher in those with abnormal parameters (OR 4.0, 95% CI 1.7-9.2, p < 0.01) when compared to normal parameters. The rate of resolution of fetal growth restriction was higher in the normal biometric parameter group compared to those with abnormal parameters (OR 3.3, 95% CI 1.4-8.1, p < 0.01).

CONCLUSIONS

Fetal growth restriction and normal biometric parameters diagnosed at second trimester ultrasound is associated with an increased likelihood of resolution of growth restriction and decreased likelihood of delivering a small for gestational age neonate.