Detection and clinical outcome of small-for-gestational-age fetuses in the third trimester-A comparison between routine ultrasound examination and examination on indication

Routine third-trimester ultrasound assessment for intrauterine growth restriction

Intrauterine growth restriction significantly impacts perinatal outcomes. Undetected IUGR escalates the risk of adverse outcomes. Serial symphysis-fundal height measurement, a recommended strategy, is insufficient in detecting abnormal fetal growth. Routine third-trimester ultrasounds significantly improve detection rates compared with this approach, but direct high-quality evidence supporting enhanced perinatal outcomes from routine scanning is lacking. In assessing fetal growth, abdominal circumference alone performs comparably to estimated fetal weight. Hadlock formulas demonstrate accurate fetal weight estimation across diverse gestational ages and settings. When choosing growth charts, prescriptive standards (encompassing healthy pregnancies) should be prioritized over descriptive ones. Customized fetal standards may enhance antenatal IUGR detection, but conclusive high-quality evidence is elusive. Emerging observational data suggest that longitudinal fetal growth assessment could predict adverse outcomes better. However, direct randomized trial evidence supporting this remains insufficient.

Screening for small for gestational age infants in early vs late third-trimester ultrasonography: a randomized trial

BACKGROUND

Recent studies have demonstrated that a routine third-trimester ultrasound scan may improve the detection of small for gestational age infants when compared with clinically indicated ultrasound scans but with no reported reduction in severe perinatal morbidity. Establishing the optimal gestational age for the third-trimester examination necessitates evaluation of the ability to detect small for gestational age infants and to predict maternal and perinatal outcomes. Intrauterine growth restriction most often corresponds with small for gestational age infants associated with pathologic growth patterns.

OBJECTIVE

This study aimed to assess the performance of routine early ultrasound scans vs late ultrasound scans during the third trimester of pregnancy to identify small for gestational age infants and fetuses with intrauterine growth restriction.

STUDY DESIGN

This was an open-label, randomized, parallel trial conducted in Upper Normandy, France, from 2012 to 2015. The study eligibility criteria were heathy, nulliparous women older than 18 years with gestational age determined using the crown-rump length at the first trimester routine scan and with no fetal malformation or suspected small for gestational age fetus at the routine second trimester scan. Pregnant women were randomly assigned to a third-trimester scan group at 31 weeks gestational age ±6 days (early ultrasound scan) or at 35 weeks gestational age ±6 days (late ultrasound scan). The primary outcome of this trial was the ability of a third trimester scan to predict small for gestational age infants (customized birth weight <10th percentile) and intrauterine growth restriction (customized birth weight

RESULTS

Results from 1853 women assigned to the early ultrasound scan group and 1848 women assigned to the late ultrasound scan group were analyzed. The sensitivity was found to be higher in the late ultrasound scan group than in the early ultrasound scan group, both for identifying small for gestational age infants (27%; 22%-32% vs 17%; 13%-22%; P=.004) and intrauterine growth restriction (44%; 35%-54% vs 18%; 11%-27%; P<.001). There was little difference in the specificity between the late ultrasound scan and early ultrasound scan groups in identifying cases of small for gestational age (97%; 96%-98% and 98%; 97%-99%, respectively; P=.04) and intrauterine growth restriction (96%; 95%-97% and 97%; 96%;-97%, respectively; P=.24). Overall, the maternal and neonatal outcomes were comparable between the early ultrasound scan and late ultrasound scan groups with the exception of additional (at least 1) ultrasound scans performed (25% in the early ultrasound scan group vs 19% in the late ultrasound scan group; P<.001). Rates of perinatal death (0.4% vs 0.8%; P=.12) and adverse perinatal outcomes (1.8% vs 2.7%; P=.08) were comparable between the early ultrasound scan and late ultrasound scan assigned groups, and the overall sensitivity to detect small for gestational age infants and intrauterine growth restriction, including in the last ultrasound scan performed before delivery, were also similar (30%; 25%-36% vs 26%; 21%-31%; P=.23; and 50%; 40%-60% vs 38%; 28%-48%; P=.07).

CONCLUSION

A late ultrasound scan performed in the third trimester increases the probability of detecting small for gestational age infants and intrauterine growth restriction with fewer additional scans reported than for the early ultrasound scan group. The overall perinatal outcome risk was comparable between the 2 groups. However, the overall sensitivity for detecting small for gestational age fetuses and intrauterine growth restriction, including in the last ultrasound scan performed before delivery, remains comparable between the late ultrasound scan and early ultrasound scan groups.

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Key Words

• intrauterine growth restriction
• perinatal mortality and morbidity
• screening
• small for gestational age
• ultrasonography

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MESH Headings

• Female
• Humans
• Pregnancy
• Birth Weight
• Fetal Growth Retardation/diagnostic imaging
• Fetal Growth Retardation/epidemiology
• Gestational Age
• Pregnancy Trimester, Third
• Ultrasonography, Prenatal/methods

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Affiliation(s)

Eric Verspyck Department of Obstetrics and Gynecology, Rouen University Hospital, Rouen, France (Drs Verspyck, Brasseur-Daudruy, Braund, and Benichou).
Caroline Thill Department of Biostatistics, Rouen University Hospital, Rouen, France (Dr Thill)
Anne Ego University Grenoble Alpes, CNRS, Public Health Department CHU Grenoble Alpes, Grenoble Institute of Engineering, TIMC-IMAG, 38000 Grenoble, France (Dr Ego); INSERM UMR 1153, Obstetrical, Perinatal and Pediatric Epidemiology Research Team (EPOPé), Center for Epidemiology and Statistics Sorbonne Paris Cité (CRESS), FHU PREMA, Paris Descartes University, Paris, France (Dr Ego)
Elise Machevin Department of Obstetrics and Gynecology, Evreux Hospital, Evreux, France (Dr Machevin)
Marie Brasseur-Daudruy Department of Obstetrics and Gynecology, Rouen University Hospital, Rouen, France (Drs Verspyck, Brasseur-Daudruy, Braund, and Benichou)
Valentine Ickowicz Department of Obstetrics and Gynecology, Belvedere Hospital, Mont Saint Aignan, France (Dr Ickowicz)
Caroline Blondel Department of Obstetrics and Gynecology, Mathilde Private Clinic, Rouen, France (Dr Blondel)
Sophie Degré Department of Obstetrics and Gynecology, Le Havre Hospital, Le Havre, France (Dr Degré)
Anne Lefebure Department of Obstetrics and Gynecology, Elbeuf Hospital, Elbeuf, France (Dr Lefebure)
Sophia Braund Department of Obstetrics and Gynecology, Rouen University Hospital, Rouen, France (Drs Verspyck, Brasseur-Daudruy, Braund, and Benichou)
Jacques Benichou Department of Obstetrics and Gynecology, Rouen University Hospital, Rouen, France (Drs Verspyck, Brasseur-Daudruy, Braund, and Benichou); Inserm U1018, University of Rouen and University Paris-Saclay, Rouen, France (Dr Benichou); Department of Biostatistics, Rouen University Hospital, Rouen, France (Dr Benichou)

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The association between undetected small-for-gestational age and abnormal admission cardiotocography: A registry-based study

OBJECTIVE

To assess the association between undetected small-for-gestational age (SGA) fetuses and abnormal admission cardiotocography (admCTG) in a low-risk population.

DESIGN

An observational study.

SETTING

Four hospitals in Stockholm-Gotland, Sweden.

SAMPLE

A cohort of 127 461 deliveries between 1 February 2012 and 15 June 2020.

METHODS

This cohort was linked to the Swedish Neonatal Quality Register. Pregnancies were designated as high or low risk at the time of admission to the labour ward according to pre-defined risk measures. SGA was defined as a birthweight at or below the tenth centile and at or below the third centile for gestational age.

MAIN OUTCOME MEASURES

The main outcome was the proportion of undetected SGA by admCTG (normal or abnormal). The secondary outcome was a composite severe adverse neonatal outcome for fetuses born less than 6 hours after admission (Apgar score <4 at 5 minutes, hypoxic-ischaemic encephalopathy grade of 2-3, neonatal seizures and neonatal death).

RESULTS

The rate of abnormal admCTG was 4.9%. The proportion of SGA at or below the tenth centile was higher in the abnormal admCTG group than in the normal admCTG group, 18.6% versus 9.7% (odds ratio 2.1, 95% CI 1.9-2.3). Abnormal admCTG and SGA (≤10th) was associated with a more than 20-fold increased risk of an adverse outcome compared with normal admCTG and non-SGA (adjusted odds ratio 23.7, 95% CI 9.8-57.3). The latter had a risk of 1/2000 of an adverse outcome.

CONCLUSIONS

In this low-risk population, undetected SGA fetuses were more prone to having abnormal admCTG and had a substantially higher risk of severe adverse neonatal outcomes.

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.