Maternal antenatal corticosteroids for late preterm infants

Late preterm birth, defined in Australia as birth from 34+0 to 36+6 weeks of gestation, sits between apparent maturity and genuine physiological vulnerability. These newborns may look well initially, yet still develop respiratory distress, feeding difficulty, temperature instability, jaundice, or low blood glucose after birth. Decisions made before delivery can influence how smoothly that transition occurs.

Antenatal corticosteroids, usually betamethasone, accelerate aspects of fetal lung maturation. The treatment is most relevant when there is a substantial chance of birth within the next seven days, rather than as a routine intervention for every pregnancy approaching 37 weeks. Timing, indication, infection risk, diabetes, gestational age, and the availability of neonatal care all matter.

The subject also sits within a wider perinatal evidence base involving preterm birth prevention, group B streptococcus management, neonatal respiratory support, and parent counselling. The historical FAOPS 2020 archive reflects the international scientific setting in which these questions were being discussed, including the congress planned for Tokyo before it was cancelled during the COVID-19 pandemic.

Why late preterm birth needs separate thinking

Late preterm infants account for a substantial proportion of premature births. Their outcomes are generally better than those of very preterm babies, but their risk is higher than that of term newborns. A 35-week infant may require admission to a special care nursery for continuous monitoring, oxygen, intravenous fluids, or feeding support even when the birth appears uncomplicated.

The reason for caution is that lung maturity does not progress in a simple switch from “immature” to “mature.” Surfactant production, alveolar development, respiratory drive, airway stability, and the ability to coordinate sucking and swallowing continue to develop during the final weeks of pregnancy. Corticosteroids can improve pulmonary adaptation, but they cannot remove every late preterm risk.

The cause and timing of planned birth should shape the conversation. Pre-eclampsia, fetal growth restriction, antepartum bleeding, ruptured membranes, cholestasis, diabetes, multiple pregnancy, and maternal or fetal compromise carry different balances of benefit and harm. Delaying birth to complete steroids may be inappropriate when urgent delivery is safer for the mother or baby.

Australian geography adds a practical dimension. A family in Darwin, rural Queensland, or regional Western Australia may face a transfer to a tertiary unit, while a patient in Melbourne or Sydney may have several neonatal services within a shorter distance. The likely place of birth and the time required to reach higher-level care should be included in planning.

What evidence says about steroids

The landmark Antenatal Late Preterm Steroids trial found that a course of betamethasone reduced the need for respiratory support in infants born late preterm when delivery was expected within seven days. Benefits included fewer cases requiring continuous positive airway pressure or other respiratory assistance. This evidence changed practice in many countries, including Australia, although local policies differ in their wording and thresholds.

The main short-term trade-off is neonatal hypoglycaemia. Babies exposed to antenatal corticosteroids need glucose surveillance according to local newborn protocols, especially when they are small, late preterm, large for gestational age, or born to a mother with diabetes. Hypoglycaemia is often treatable, but it can require early feeds, buccal glucose gel, intravenous dextrose, and separation from the parent if higher-level monitoring is needed.

Evidence for longer-term outcomes is more limited than evidence for short-term respiratory effects. Follow-up studies have not established a clear major developmental harm from a single indicated course, but uncertainty remains, particularly for repeated exposure, administration at earlier gestations, or treatment when birth does not occur soon afterwards. Clinicians should avoid presenting steroids as risk-free or as a guarantee that intensive care will not be needed.

A single course generally means two intramuscular doses of betamethasone 24 hours apart, depending on the product and hospital protocol. If delivery occurs before the course is complete, the first dose may still be worthwhile when clinically appropriate. Treatment should never postpone an urgent birth merely to complete the schedule.

How Australian teams should assess eligibility

Assessment begins with a realistic estimate of birth within seven days. Cervical change, regular preterm contractions, preterm prelabour rupture of membranes, planned caesarean birth for a clear indication, worsening maternal disease, and fetal concerns may support treatment. A vague possibility of early birth several weeks in the future is a weaker indication and exposes more patients to treatment without a clear immediate benefit.

Gestational age must be confirmed as accurately as possible, using the best available dating information. Teams should check whether the patient has already received a course, whether there is suspected intra-amniotic infection, and whether the anticipated delivery is medically necessary now. Repeat courses are not automatically appropriate and require specialist review because cumulative exposure changes the risk discussion.

Infection assessment is particularly important with ruptured membranes or suspected chorioamnionitis. Steroids do not replace antibiotics, delivery planning, or neonatal infection observation. Group B streptococcus prevention has its own indications and timing; the practical relationship between screening, intrapartum antibiotics, and newborn assessment is outlined in these GBS screening updates.

Consent should cover both sides of the decision in plain language. Parents need to know that steroids may reduce breathing support, while the baby may be more likely to have low glucose and may still require special care nursery admission. In Australia, discussions should also account for Aboriginal and Torres Strait Islander families, interpreters, transport, cultural safety, and whether transfer away from Country or family support is likely.

Safety monitoring after birth

The neonatal plan should be agreed before the medication is given. Staff should document gestational age, the time and dose of each injection, the indication, diabetes status, rupture of membranes, infection concerns, and the intended place of birth. This information prevents repeated treatment and helps the receiving neonatal team interpret early symptoms.

Respiratory observation should include work of breathing, oxygen saturation, respiratory rate, and signs of exhaustion or apnoea. A late preterm infant may initially appear stable and then deteriorate during the first hours. Continuous positive airway pressure, nasal high-flow therapy, chest imaging, and transfer arrangements should be available according to the level of care.

Glucose monitoring needs to be paired with a feeding plan. Early skin-to-skin contact, expressed colostrum, breastfeeds, donor milk, or formula may all have a role depending on the clinical situation and family preference. Australian hospitals commonly use formal late preterm pathways covering glucose checks, temperature, weight, feeding effectiveness, jaundice, and discharge criteria.

Discharge should be based on function rather than a particular day of life. The newborn should maintain temperature, feed safely, show acceptable glucose results, and have a follow-up plan for weight, jaundice, and feeding. Families should receive clear instructions about poor feeding, unusual sleepiness, breathing difficulty, reduced wet nappies, and when to seek urgent help through local maternity services or emergency care.

Practical recommendations for maternity services

A consistent pathway reduces variation between obstetric, midwifery, neonatal, and paediatric teams. It should define the gestational age range, likely-delivery criteria, contraindications, consent process, glucose surveillance, and escalation arrangements. Pathways also need review as national guidance and local neonatal capacity change.

Hospitals should audit both treatment and outcomes. Useful measures include the proportion of eligible patients receiving steroids, the interval between treatment and birth, respiratory support, hypoglycaemia requiring intervention, neonatal admission, readmission for feeding or jaundice, and documented parent counselling. Data should be interpreted carefully because the pregnancies receiving steroids may already have higher baseline risk.

Practical priorities include:

• Offer a single course when late preterm birth within seven days is sufficiently likely and no urgent contraindication exists.
• Do not delay medically necessary delivery solely to complete corticosteroid dosing.
• Document prior exposure, maternal diabetes, infection assessment, gestational age, and the planned neonatal glucose pathway.
• Coordinate obstetric, midwifery, neonatal, anaesthetic, retrieval, and primary care services before delivery.
• Use culturally safe counselling and provide accessible written information for families from metropolitan, regional, remote, and First Nations communities.

For Australian maternity services, the most effective approach is a shared decision pathway that connects antenatal assessment with newborn care. Clinicians can review local guidance, check current evidence, and discuss each family’s circumstances before prescribing. Parents should leave the conversation understanding why treatment is being considered, what it may achieve, and how the baby will be monitored afterwards.

Use the evidence to update hospital protocols, educate multidisciplinary teams, and strengthen links between metropolitan centres and regional referral services. Thoughtful selection of patients, prompt communication, and reliable neonatal monitoring allow antenatal corticosteroids to be used where their benefits are most likely to outweigh their risks.