Antenatal Steroids: Are They Always a Safe Bet for Premature Babies?
"A new study suggests that while antenatal corticosteroids can benefit some premature babies, they may pose risks for those with growth restrictions."
For women at risk of premature delivery, antenatal corticosteroids (ACS) are a standard treatment to help speed up the development of the baby's lungs. However, new research suggests that while ACS can be beneficial, it may not be a one-size-fits-all solution, especially for growth-restricted (GR) fetuses.
A study published in 'Ultraschall in Med' investigates how ACS affects blood flow and heart function in both appropriate for gestational age (AGA) and growth-restricted fetuses. The findings reveal that while ACS can improve some blood flow parameters, it may also lead to potential heart function issues in GR fetuses.
This article will delve into the key findings of this research, explore the implications for prenatal care, and offer guidance for parents and healthcare providers navigating the complexities of premature birth interventions.
Established Use and Evidence Limits
Antenatal corticosteroids are standard practice for impending preterm delivery before 34 weeks of gestation, and evidence from randomized controlled trials indicates reductions in neonatal mortality and morbidity, including respiratory distress and cerebrovascular haemorrhage. The WHO recommendations supersede its 2015 guidance on interventions to improve preterm birth outcomes. WHO's Guideline Development Group noted that the lower gestational-age limit was based on available trial evidence, while observational evidence suggests corticosteroids may provide substantial clinical benefits for infants born before 24 weeks. This means evidence is strongest within studied gestational-age ranges, while use at the earliest gestations relies more heavily on observational data.
Understanding the Study: ACS Impact on Fetal Cardiovascular Health
The study, led by Laura Marchi and colleagues, involved monitoring cardiovascular function in AGA and GR fetuses before and after ACS administration. Using Doppler ultrasound, researchers assessed various parameters, including:
- Cardiac Function: Assessed through the ductus venosus (DV) PI, E/A wave ratios, and myocardial performance index (MPI).
- Study Timeline: Measurements were taken before ACS, 24-48 hours after the first dose, and seven days after the second dose.
New Directions in Cardiac Research
Recent research is examining cardiovascular effects alongside the established neonatal benefits of antenatal corticosteroids. A systematic review and meta-analysis found that fetuses with small-for-gestational age status had a significantly higher mean left fetal myocardial performance index than controls, with a weighted mean difference of 0.09 and substantial heterogeneity (I²=97%). In a sheep model, researchers compared low-dose steroid therapy of 10 mg delivered over 36 hours with a higher 30 mg dose delivered over 24 hours by intramuscular injection. A separate quasi-experimental before-after study assessed short-term fetal cardiovascular and circulation effects in 32 singleton fetuses.
Questions Beyond Immediate Benefit
The evidence base does not settle every question about antenatal corticosteroid exposure. Neurological research has evaluated outcomes among late-preterm or term-born groups exposed to preterm labor and antenatal corticosteroids, alongside comparison groups exposed to preterm labor without corticosteroids. A 2025 overview of systematic reviews noted that antenatal corticosteroids reduce neonatal mortality and short-term morbidities when given to women at risk of birth before 34 weeks, but said long-term child-health evidence had not been comprehensively assessed. Other research has examined associations after dexamethasone exposure and the extension of corticosteroid use beyond 34 weeks since 2015.
Ductus Venosus Blood Flow
One comparative study examined the relationship between ductus venosus blood flow and chronic fetal distress. It included 100 pregnant women between 37 and 41 weeks of gestation. The participants were divided into a control group of 50 women and a chronic fetal distress group of 50 women. The available source description identifies the study design and groups but does not provide its comparative findings.
Making Informed Decisions About Antenatal Steroids
While ACS remains a crucial tool in managing preterm births, this study highlights the importance of considering individual fetal conditions, especially in growth-restricted fetuses. Parents and healthcare providers should engage in thorough discussions about the potential risks and benefits of ACS, ensuring the best possible outcomes for both mother and child. Further research is needed to refine these findings and develop more targeted interventions for high-risk pregnancies.
More Targeted Treatment
Antenatal steroid therapy is described as standard care for women likely to deliver between 24 and 34 weeks' gestation. The treatment is reported to provide sizable benefits and few risks in high-resource environments when appropriately targeted. Recent studies have focused on antenatal steroid use beyond these established circumstances. The next research questions therefore include how best to target treatment as its use expands.
Metabolic and High-Risk Groups
Antenatal corticosteroid research includes attention to cortisol and blood-glucose effects in premature infants. One study specifically identifies hypoglycemia risk as part of the neonatal-care context surrounding corticosteroid exposure. Another study examined mortality and morbidity among small-for-gestational-age infants born at 24 to 34 completed weeks in a retrospective multicenter design. These findings highlight the need to consider metabolic effects and infant subgroups when applying antenatal corticosteroid protocols.
Benefits Depend on Circumstances
Antenatal dexamethasone has been studied as an intervention for early preterm birth in low-resource settings. Other research notes that antenatal corticosteroids are widely used to reduce respiratory distress in preterm infants, while less is known about short-term neonatal risks when exposure occurs in pregnancies that ultimately result in term delivery. That research also examines whether gestational age at exposure affects outcomes. The potential real-world impact therefore depends on the timing of treatment and whether preterm birth actually occurs.