Key takeaways
Steroid injections in pregnancy can help babies’ lungs mature if birth is expected early
The strongest evidence of benefit is when babies are likely to be born very preterm
For births after around 35 weeks, and for twins, the balance of benefits and drawbacks is less clear
Your care team should talk you through the potential pros and cons so you can decide what feels right for you
Steroid injections in pregnancy: what they are
Steroids are human-made versions of hormones that our bodies naturally produce. One example is cortisol, which your body makes when you’re under stress. In pregnancy care, you might hear steroid injections called ‘corticosteroids’.
When steroids are given during pregnancy, they’re usually referred to as antenatal corticosteroids, often shortened to ACS. These medicines are used in lots of areas of healthcare. You may have come across steroid inhalers for asthma, injections for arthritis or creams for skin conditions like eczema.
In obstetric care (pregnancy care), steroid injections are most often discussed when there’s a concern that a baby might be born early. This could be because your team is worried about your health, your babies’ health, or because a birth is being planned earlier than expected. Sometimes steroids are also offered when someone is thought to be in preterm labour or at higher risk of going into labour soon.
Predicting preterm labour is difficult. It can be stressful to be asked to make decisions when nobody can be completely certain what will happen next. You deserve clear information and time to talk things through.
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How antenatal steroids may help your babies
The main reason ACS are offered is to support babies’ lung development. Steroids can cross the placenta and help the lungs mature. This may lower the chance of breathing difficulties after birth and reduce how much breathing support a baby needs in a neonatal unit.
In singleton pregnancies where birth happens very early, there’s clear evidence that antenatal steroids reduce the chance of a baby dying or having serious breathing problems. Because of this, they’re routinely offered when a baby is expected to be born very preterm, often before 35 weeks of pregnancy.
The picture becomes less straightforward later in pregnancy. Evidence about ACS between 35 and 39 weeks is less clear. Babies born before full term (before 37 weeks) are still more likely to have breathing problems after birth, and they’re more likely to need neonatal support. This risk can be higher if they’re born by caesarean section. Some evidence suggests antenatal steroids can still reduce breathing problems at these gestations, which is why some doctors offer or recommend ACS up to 37 weeks, and up to 39 weeks before a planned caesarean section.
Steroids and twins: why the decision can feel harder
If you’re expecting twins, triplets or more, you may find steroid injections come up more often. That’s because multiples are more likely to be born before 37 weeks. Even being born slightly early can increase the chance of babies needing breathing support in hospital.
For many parents, one of the hardest parts is the possibility of separation. If your babies need neonatal care, it can mean time apart at a point when you want to be together, recovering and getting to know each other.
At the same time, twins have been less well studied in this area. We have less information about the risks and benefits of ACS for twins across all gestations. That makes it harder to weigh things up with confidence.
Recent evidence has also raised questions about possible unwanted effects. These may include babies having lower blood sugars after birth and possible effects on growth. We don’t yet know how common these side effects are, or whether they outweigh the potential benefits in later gestations.
Some population studies have suggested that babies who received steroids before birth but were delivered at full term are slightly more likely to have additional needs, including ADHD, learning difficulties and autism. These conditions are common, and it’s not clear whether the steroids are directly linked. It may be that steroids are more often given in pregnancies where there are already higher risks of complications, including factors that could affect brain development. There’s very little information from these studies that’s specific to twins.
Because the evidence is limited, there isn’t currently clear guidance on giving ACS in twin pregnancies. That means practice can vary between hospitals.
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Making an informed choice with your maternity team
The Royal College of Obstetricians and Gynaecologists advises that after 34 weeks, doctors should discuss the potential benefits and possible drawbacks before giving ACS. That’s so you can make an informed choice, especially when the evidence isn’t clear-cut.
If steroids are being offered, it can help to ask your team to explain what they think the main benefit is for your situation, and what the uncertainties are. You can also ask what monitoring your babies might need after birth, such as checks for low blood sugars, and how neonatal support would work if it’s needed.
There isn’t always a simple ‘right’ answer here. What matters is that you feel listened to, you understand why steroids are being suggested, and you’re supported to make the decision that feels best for you and your family.
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