From the Guidelines
Fetuses with intrauterine growth restriction (IUGR) are at risk for several adverse neonatal outcomes after birth, including stillbirth, severe acidosis, low 5-minute Apgar scores, and neonatal intensive care unit admissions.
Possible Adverse Neonatal Outcomes
- Stillbirth: The stillbirth rate is approximately 1.5% in fetuses with weights below the 10th percentile, which is twice the rate in fetuses with normal growth 1.
- Severe acidosis at birth: Infants with birthweights below the 10th percentile are more likely to have severe acidosis at birth 1.
- Low 5-minute Apgar scores: Infants with birthweights below the 10th percentile are more likely to have low 5-minute Apgar scores 1.
- Neonatal intensive care unit admissions: Infants with birthweights below the 10th percentile are more likely to have neonatal intensive care unit admissions 1.
Severity of Fetal Growth Restriction
The severity of fetal growth restriction is a significant predictor of adverse perinatal outcomes. An estimated fetal weight (EFW) below the third percentile has been associated with an increased risk of adverse perinatal outcome, irrespective of umbilical and middle cerebral artery Doppler indices 1.
Management of Fetal Growth Restriction
Management of fetal growth restriction is based on early diagnosis, optimal fetal surveillance, and timely delivery that reduces perinatal mortality and minimizes short- and long-term morbidity 1. The decision to deliver is typically guided by maternal factors, such as the presence of maternal hypertension, and by fetal comorbidities, such as the degree of growth restriction and the severity of abnormal fetal surveillance results.
Fetal Surveillance
Fetal surveillance is essential in the management of pregnancies with fetal growth restriction. This includes regular assessment of fetal biometry, evaluation of amniotic fluid volume, use of the biophysical profile (BPP), Doppler US, fetal heart rate monitoring, especially the nonstress test (NST), and fetal movement counting 1.
Doppler Assessment
Doppler assessment of the fetus with intrauterine growth restriction is crucial in predicting adverse perinatal outcomes. The presence of abnormal umbilical artery Doppler indices has been found to predict adverse perinatal outcomes 1.
From the Research
Adverse Neonatal Outcomes of IUGR
The possible adverse neonatal outcomes of fetuses with intrauterine growth restriction (IUGR) after birth include:
- Increased mortality 2, 3, 4
- Increased morbidity 2, 3, 5, 4
- Necrotizing enterocolitis 2, 5
- Respiratory distress syndrome (RDS) 5
- Intraventricular hemorrhage (IVH) 5
- Retinopathy of the premature 2
- Need for respiratory support at 28 days of age 2
- Chronic diseases in adulthood, such as respiratory, cardiovascular, and neurological disorders 3
- Impaired innate immune system, including diminished white blood cells, neutrophils, and platelet counts, as well as altered cytokine immune responses 6
- Increased risk of bronchopulmonary dysplasia 6
Gestational Age-Specific Associations
The associations between IUGR and adverse neonatal outcomes vary by gestational age:
- At earlier gestational ages (≤28 weeks), the incidence of RDS, IVH, and NEC may be higher in infants without IUGR compared to those with IUGR 5
- At later gestational ages (≥29 weeks), the incidence of RDS, IVH, and NEC is higher in infants with IUGR compared to those without IUGR 5
- The threshold at which the relationship between IUGR and adverse outcomes flips is around 29-30 weeks of gestation 5
Clinical Management
Prenatal identification of IUGR is crucial for clinical management, and a uniform definition and criteria are required 4. The timing of delivery is critical, and careful monitoring of the IUGR fetus during labor is essential to prevent decompensation 4. Delivery of IUGR fetuses should take place in centers with appropriate neonatal assistance 4.