Current practice in the diagnosis and management of fetal growth restriction: An international survey

Fetal size vs growth: comparative analysis of 3 models of growth velocity based on third trimester estimated fetal weights for identifying stillbirth risk

BACKGROUND

Fetal growth velocity is being recognized as an important parameter by which to monitor fetal wellbeing, in addition to assessment of fetal size. However, there are different models and standards in use by which velocity is being assessed.

OBJECTIVE

We wanted to investigate 3 clinically applied methods of assessing growth velocity and their ability to identify stillbirth risk, in addition to that associated with small for gestational age.

STUDY DESIGN

Retrospective analysis of prospectively recorded routine-care data of pregnancies with 2 or more third trimester scans in New Zealand. Results of the last 2 scans were used for the analysis. The models investigated to define slow growth were (1) 50+ centile drop between measurements, (2) 30+ centile drop, and (3) estimated fetal weight below a projected optimal weight range, based on predefined, scan interval specific cut-offs to define normal growth. Each method's ability to identify stillbirth risk was assessed against that associated with small-for-gestational age at last scan.

RESULTS

The study cohort consisted of 71,576 pregnancies. The last 2 scans in each pregnancy were performed at an average of 32+1 and 35+6 weeks of gestation. The 3 models defined "slow growth" at the following differing rates: (1) 50-centile drop 0.9%, (2) 30-centile drop 5.1%, and (3) below projected optimal weight range 10.8%. Neither of the centile-based models identified at-risk cases that were not also small for gestational age at last scan. The projected weight range method identified an additional 79% of non-small-for-gestational-age cases as slow growth, and these were associated with a significantly increased stillbirth risk (relative risk, 2.0; 95% CI, 1.2-3.4).

CONCLUSION

Centile-based methods fail to reflect adequacy of fetal weight gain at the extremes of the distribution. Guidelines endorsing such models might hinder the potential benefits of antenatal assessment of fetal growth velocity. A new, measurement-interval-specific projection model of expected fetal weight gain can identify fetuses that are not small for gestational age, yet at risk of stillbirth because of slow growth. The velocity between scans can be calculated using a freely available growth rate calculator (www.perinatal.org.uk/growthrate).

The role of the PLGF in the prediction of the outcome in pregnancies with a small for gestational age fetus

PURPOSE

To explore the value of measuring maternal serum PLGF in the prediction of the outcome of small for gestational age fetuses (SGA).

METHODS

Singleton pregnancies referred with suspicion of SGA in the third trimester were included if they had: no indication for nor signs of imminent delivery, fetal abdominal circumference (AC) at or below the 10th centile and/or estimated fetal weight (EFW) at or below the 10th centile and/or umbilical artery pulsatility index (Umb-PI) at or above the 90th centile for gestation. Women with pre-eclampsia at presentation were excluded. Maternal blood was drawn at the first (index) visit and analyzed retrospectively.

RESULTS

Fifty-one fetuses were examined. Multiple regression analysis showed that family history of microsomia, index EFW and PLGF were significant predictors of the birthweight centile; index femur length centile and PLGF were significant predictors of pre-eclampsia; PLGF and index systolic blood pressure were significant predictors of iatrogenic preterm delivery < 37 weeks, whereas PLGF and index EFW were significant predictors of birthweight ≤ 5th centile and admission to the neonatal intensive care unit. For all outcomes, the addition of maternal-fetal parameters did not improve the prediction compared to PLGF alone. Using a cutoff of 0.3 MoM for PLGF would identify 94.1% of the pregnancies with iatrogenic preterm delivery and/or intra-uterine death and all of the cases that developed pre-eclampsia, for a screen positive rate of 54.9%. Women with PLGF ≤ 0.3 MoM had a poor fetal/maternal outcome (iatrogenic preterm delivery, pre-eclampsia, intra-uterine death) in 61.5% of cases.

CONCLUSION

In pregnancies complicated by SGA, PLGF identifies a very high-risk group that may benefit from intense surveillance.

Intrauterine Growth Restriction: Need to Improve Diagnostic Accuracy and Evidence for a Key Role of Oxidative Stress in Neonatal and Long-Term Sequelae

Intrauterine growth restriction (IUGR) and being small for gestational age (SGA) are two distinct conditions with different implications for short- and long-term child development. SGA is present if the estimated fetal or birth weight is below the tenth percentile. IUGR can be identified by additional abnormalities (pathological Doppler sonography, oligohydramnion, lack of growth in the interval, estimated weight below the third percentile) and can also be present in fetuses and neonates with weights above the tenth percentile. There is a need to differentiate between IUGR and SGA whenever possible, as IUGR in particular is associated with greater perinatal morbidity, prematurity and mortality, as well as an increased risk for diseases in later life. Recognizing fetuses and newborns being "at risk" in order to monitor them accordingly and deliver them in good time, as well as to provide adequate follow up care to ameliorate adverse sequelae is still challenging. This review article discusses approaches to differentiate IUGR from SGA and further increase diagnostic accuracy. Since adverse prenatal influences increase but individually optimized further child development decreases the risk of later diseases, we also discuss the need for interdisciplinary follow-up strategies during childhood. Moreover, we present current concepts of pathophysiology, with a focus on oxidative stress and consecutive inflammatory and metabolic changes as key molecular mechanisms of adverse sequelae, and look at future scientific opportunities and challenges. Most importantly, awareness needs to be raised that pre- and postnatal care of IUGR neonates should be regarded as a continuum.

Outcome-based comparative analysis of five fetal growth velocity models to define slow growth

OBJECTIVE

Fetal growth surveillance includes assessment of size as well as rate of growth, and various definitions for slow growth have been adopted into clinical use. The aim of this study was to evaluate the effectiveness of different models to identify stillbirth risk, in addition to risk represented by the fetus being small-for-gestational age (SGA).

METHODS

This was a retrospective analysis of a routinely collected and anonymized dataset of pregnancies that had two or more third-trimester ultrasound measurements of estimated fetal weight (EFW). SGA was defined as EFW < 10th customized centile, and slow growth was defined according to five published models in clinical use: (1) a fixed velocity limit of 20 g per day (FVL20 ); (2) a fixed > 50 centile drop, regardless of scan-measurement interval (FCD50 ); (3) a fixed > 30 centile drop, regardless of scan interval (FCD30 ); (4) growth trajectory slower than the third customized growth-centile limit (GCL3 ); and (5) EFW at second scan below the projected optimal weight range (POWR), based on partial receiver-operating-characteristics-curve-derived  cut-offs specific to the scan interval.

RESULTS

The study cohort consisted of 164 718 pregnancies with 480 592 third-trimester ultrasound scans (mean ± SD, 2.9 ± 0.9). The last two scans in each pregnancy were performed at an average gestational age of 33 + 5 and 37 + 1 weeks. At the last scan, 12 858 (7.8%) EFWs were SGA, and of these, 9359 were also SGA at birth (positive predictive value, 72.8%). The rate at which slow growth was defined varied considerably (FVL20 , 12.7%; FCD50 , 0.7%; FCD30 , 4.6%; GCL3 , 19.8%; POWR, 10.1%), and there was varying overlap between cases identified as having slow growth and those identified as SGA at the last scan. Only the POWR method identified additional non-SGA pregnancies with slow growth (11 237/16 671 (67.4%)) that had significant stillbirth risk (relative risk, 1.58 (95% CI, 1.04-2.39)). These non-SGA cases resulting in stillbirth had a median EFW centile of 52.6 at the last scan and a median weight centile of 27.3 at birth. Subgroup analysis identified methodological problems with the fixed-velocity model because it assumes linear growth throughout gestation, and with the centile-based methods because the non-parametric distribution of centiles at the extremes does not reflect actual difference in weight gain.

CONCLUSION

Comparative analysis of five clinically used methods to define slow fetal growth has shown that only the measurement-interval-specific POWR model can identify non-SGA fetuses with slow growth that are at increased risk of stillbirth. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.