Can we safely reduce the risk of breathing problems for newborn babies by giving corticosteroid injections to their mothers before a planned caesarean section?

What is The C*STEROID Trial?

We are carrying out the C*STEROID Trial to find out whether giving mothers corticosteroid injections before having a planned caesarean section at 35 – 39+6 weeks of pregnancy will safely reduce the risk of short term breathing problems for babies. This trial will include over 2,500 mothers and their babies.

Why is The C*STEROID Trial important?

In New Zealand around 7500 babies are born by planned (also known as elective or pre-labour) caesarean section each year. Whichever way women birth there are some advantages and disadvantages for mother and baby, and this includes some disadvantages to planned caesarean section. Babies born by caesarean section before labour has started are more likely to experience short term breathing problems compared to babies born by vaginal delivery or by caesarean section after labour has started. While the overall risk of these breathing problems is low after 35 weeks gestation, we would like to assess whether giving mothers injections of corticosteroid can safely reduce this risk. If this is shown to be safe and effective it may decrease the number of babies needing breathing support and being admitted to the neonatal unit. We will also explore the effect of corticosteroids on the longer term development of children born to mothers who have participated in the trial.

Who can take part in the C*STEROID Trial?

The C*STEROID Trial will be conducted at a number of hospitals across New Zealand. Check whether your hospital is participating in the find out more section.

This study may be suitable for you if you are pregnant with one baby or twins and have a caesarean section planned between 35+0 and 39+6 weeks gestation at one of our participating hospitals. This study may not be suitable for you if you have diabetes (pre-existing or gestational); if your baby is very unwell; if you have taken part in the C*STEROID Feasibility Study or the C*STEROID Trial in a previous pregnancy; or if you have already received corticosteroid injections during this pregnancy to support your baby’s lung development (you can still take part if you have had oral or inhaled steroids for other reasons).

Let your midwife or obstetrician know if you’d like to take part, or contact the C*STEROID research team to register your interest.

What is involved in The C*STEROID Trial?

Participation in this study is voluntary. If you are interested in taking part you will be provided with an information sheet and consent form to read and a member of the study team at your delivery hospital will review your eligibility to take part.

If you choose to take part you will receive two injections 24 hours apart in the week before your planned caesarean section. This will be either a corticosteroid (betamethasone) or placebo (saline, ‘salt water’). You will be asked to complete questionnaires at the time you enter the study and again six weeks after birth.

Your baby will have at least three or four blood sugar tests in the first 12 hours after birth. These require a small prick on baby’s heel to collect a few drops of blood. If your baby has a low blood sugar level this will be discussed with you and they will be treated.

Information about you and your baby/babies will be collected until six weeks after birth. We will ask to contact you from time to time until your child reaches eight years of age in order to invite you to take part in future studies to assess the later health and wellbeing of your child.

Are there any risks?

This study is designed to assess the benefits and risks of antenatal corticosteroid therapy for mothers and babies. We hope to improve the care for women and their babies in the future.

We believe that corticosteroids may reduce the risk of breathing problems and admission to the neonatal unit for breathing support. Corticosteroids may alter the chance of baby having low blood sugar levels after birth. This is a relatively common problem in newborn babies. Low blood sugars can affect baby’s longer-term health, particularly if left untreated. All babies in this study will have their blood sugar levels tested after birth and they will receive treatment if necessary.  

No health benefits or significant health harms have been seen in women receiving antenatal corticosteroids. The most common side effects are discomfort or bruising at the injection site. Rarely corticosteroids may result in gastrointestinal (tummy) upset, headache or insomnia.  

Participant experiences from The C*STEROID Feasibility Study

In developing The C*STEROID Trial we conducted a one year feasibility study at three sites in New Zealand. The feasibility study had the same inclusion criteria and trial procedures, and we asked women to share their experience in a follow-up survey after birth. Overall, 86% of women said that they would take part in the study again if they were in a similar position, and the same number said that they would recommend taking part to a friend.

Find out more

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To find out more about the trial contact our Research Coordinator on 022 4311 988 or email

Participating hospitals:

Auckland Hospital/The University of Auckland:
Ph: 021 0831 4824