What are steroid injections?

Steroids are human-made versions of hormones. Humans make their own steroid-like hormones, for example cortisol, when we are stressed. You might hear steroid injections called Corticosteroids. If they are given during pregnancy, they are called Antenatal Corticosteroids, or ACS.

Steroids are used in medicine very frequently – you might know someone who has had steroid inhalers for asthma, steroid injections for arthritis, or even steroid cream for skin conditions like eczema. These are just a few examples of the many medical uses of steroids.

Within obstetrics (the field of medicine focused on pregnancy), steroid injections are often recommended if we think that a baby (or babies) are going to be born early. This might be because we have concerns about the mother or gestational parents’ health, or concerns about the baby/babies’ health and are planning the birth of the baby/babies early. Or it might be that we think someone is in preterm labour or likely to go into preterm labour. This is very difficult to predict!

Why are steriod injections offered during pregnancy?

The reason steroid injections (ACS) will be offered to a pregnant woman (or pregnant person) if we think a baby is going to be born preterm is because steroids cross the placenta and help to mature babies’ lungs which may reduce breathing difficulties and the need for high levels of respiratory (breathing) support in the neonatal unit. They are routinely used in singleton pregnancies which deliver very early (before 35 weeks of pregnancy), because there is clear evidence that they reduce the chance of the baby dying or having serious breathing problems.    

The evidence about the use of ACS between 35-39 weeks of pregnancy when babies are still early, is less clear. We know that babies born before full term (i.e. 37 weeks) are still more likely to have breathing problems after birth and therefore have a higher chance of needing support from the neonatal unit, especially if born by Caesarean section.  However, there is some evidence to suggest that ACS are still helpful and reduce the occurrence of breathing problems in babies born at these gestations too. For this reason, doctors have often offered or recommended ACS before delivery up to 37 weeks, and in the case of Caesarean section up to 39 weeks of pregnancy. 

Similarly, twin births have been less well studied and we have less information on the risks and benefits of ACS for twin babies at all gestations. This really matters because people pregnant with twins are actually more likely than people carrying single babies to need to think about having steroids! There is a greater chance of twin babies being born before 37 weeks of pregnancy. Being born slightly early means that twins are at higher risk of admission to neonatal units for support with their breathing, which separates mothers and babies at a crucial time.

Recent evidence has shown that ACS may also have some unwanted side effects such as lowering babies’ blood sugars and affecting babies’ growth. We don’t know how common these side effects are, and if they outweigh the potential benefits of antenatal steroids. Population studies have also suggested that babies who had a course of steroids before birth and 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 is unclear how much steroids are directly associated or whether steroids are more likely to be given in pregnancies at higher risk of complications and differences in brain development later in life. There is very little information in these studies specific to twins.  

Because of the lack of evidence, there is currently no guidance on giving ACS in twin pregnancies, so whether or not women pregnant with twins receive steroids as part of routine care varies depending on their hospital. The Royal College of Obstetricians and Gynaecologists advise that doctors should discuss the potential benefits of steroids (reduction in breathing trouble and neonatal unit admission) and the possible drawbacks (higher rates of low blood sugars after birth, differences in growth and brain development) before giving after 34 weeks. This is so that you can make an informed choice. It can be difficult to make a decision when the evidence is unclear! But it’s also important that you are aware of the current understanding and the knowledge gaps.

The STOPPIT-3 research study

To understand how we can best treat twins before birth, the STOPPIT-3 research study is currently recruiting across the UK. This trial aims to find out if ACS given to women with a twin pregnancy prior to a planned birth (i.e., an elective caesarean birth or induction of labour) of twins after 35 weeks of pregnancy reduces breathing difficulties in the twin babies. Pregnant women and pregnant people who agree to take part in the trial will be treated with either ACS or a placebo (dummy drug).

The STOPPIT-3 research study will compare the two groups to see if there are differences in the need for extra support after birth. If we find that the use of ACS improves health in twin babies, it could be used across the NHS straight away. If you are interested you can find out more on the study website or ask your hospital team if they are part of the study.  

Dr Rosemary Townsend, Consultant Obstetrician, NHS Lothian and Senior Research Fellow, University of Edinburgh 

Indira Kemp, Research Midwife, Edinburgh Pregnancy Research Team