UPDATED 08/05/2019. This trial is now completed
The PRISM trial is an important trial into a potential treatment for bleeding in early pregnancy, led by Professor Arri Coomarasamy, Director of the Tommy’s National Centre for Miscarriage Research.
When a woman has bleeding in early pregnancy her risk of miscarriage increases:
- 1 in 3 women have a miscarriage
- 2 in 3 women go on to carry the baby to full term.
This research trial looked at whether progesterone can prevent miscarriage in women with early pregnancy bleeding.
How was the trial carried out?
4153 women took part in the trial in 48 hospitals across the UK.
Of those who were pregnant and experienced vaginal bleeding, around half were given progesterone pessaries (400mg) to take twice a day, and the other half were given dummy tablets.
A pessary is a tablet that you insert into your vagina (similar to inserting a tampon). Women were asked to do this twice a day until 16 weeks of pregnancy.
What is progesterone?
Progesterone is a hormone that is produced before and during pregnancy to thicken the uterine lining (endometrium) and to help the mother’s body accept the growing baby. It is used during fertility treatment to prepare the lining of the uterus for the implantation of the embryo.
What did the results show?
The results showed that although the treatment did not reduce the rate of miscarriage for those with no previous miscarriages, there was a small reduction in miscarriage for those with 1-2 previous miscarriages and a big reduction in miscarriage for those with 3 or more previous miscarriages.
The overall live birth rate was 75% (1513/2025) in the progesterone group and 72% (1459/2013) in the placebo group. That 3% difference in live birth was not ‘statistically significant’ – meaning that the difference could have been due to chance.
However, when the results were split by the number of previous miscarriages that the participants had suffered, the analysis showed that:
- No previous miscarriages: the live birth rate was 74% (824/1111) in the progesterone group and 75% (840/1127) in the placebo group, ie no benefit
- 1-2 previous miscarriages: the live birth rate was 76% (591/777) in the progesterone group and 72% (534/738) in the placebo group, ie some benefit
- 3 or more previous miscarriages: the live birth rate was 72% (98/137) in the progesterone group and 57% (85/148) in the placebo group, ie substantial benefit
How do we know the results of PRISM are reliable?
PRISM is a randomised, double-blind, placebo-controlled trial. This is the gold standard for a research trials. It was carried out with more than 4,000 women, which is the number needed to be certain that the results are reliable.
Together, these two factors mean the results can be trusted and we can be confident in recommending progesterone for women who have early pregnancy bleeding and 1 or more previous miscarriages.
What is a randomised, double blind, placebo-controlled trial?
Randomised: A computer made the selection completely randomly on which women were given the treatment drug (progesterone) or a placebo – a dummy drug that has no active ingredients.
Double-blind: The women in the study weren’t told whether they were taking the active medicine or the placebo – and neither were their doctors.
Placebo-controlled: Half the women in the study had the active medicine and the other half (the controls) had the placebo. The medicine that they received looked exactly the same to them and their doctors, but a completely separate group kept a record of which women had progesterone and which had the placebo.
What does this mean for women who have bleeding in pregnancy
If you have bleeding in your current pregnancy and you have had 1 or more previous miscarriages, we recommend that you ask your doctor for the progesterone treatment.
As this research is new your doctor may not be aware of it yet, and to help you we have prepared this document that explains the background and research to them. Print this out and take it with you, or, if you don’t have a printer, show it to them on your phone.
If you have any type of bleeding in pregnancy you need to see your midwife of doctor. Find out more about the causes and treatment here.
High quality evidence
Professor Arri Coomarasamy said: “The role of progesterone in women with early pregnancy bleeding has been studied and debated for about 60 years. But what we lacked was high quality evidence. The largest study before ours had less than 200 participants; our study had more than 4000 participants and was of very high quality.
This meant we could be confident about our findings. The finding that women who are at risk of a miscarriage because of current pregnancy bleeding and a history of a previous miscarriage could benefit from progesterone treatment has huge implications for practice. This treatment could save thousands of babies who may have otherwise been lost to a miscarriage.”
Information for clinicians
95% Confidence interval
Previous history of miscarriage
Get our research updates
Tommy's funds research across the UK investigating the reasons for pregnancy complications and loss. If you're interested in being kept updated about our research and news from Tommy's, click here.
New research has revealed the benefits of giving progesterone to women with early pregnancy bleeding and a history of miscarriage.
Tommy’s spent yesterday morning at the charming Foundling Museum in London, celebrating the work of Tommy’s National Centre for Maternity Improvement alongside the opening of the museum’s new exhibition, ‘Portraying Pregnancy’.
Miscarriage and ectopic pregnancy may trigger long-term post-traumatic stress, anxiety and depression
The largest ever study into the psychological impact of miscarriage and ectopic pregnancy has shown that early-stage pregnancy loss can have a serious impact on mental health. The research was led by Professor Tom Bourne at the Tommy’s National Centre for Miscarriage Research at Imperial College London.
A pilot trial led by Tommy’s National Centre for Miscarriage Research suggests diabetes drug could be repurposed to target the lining of the womb in women with recurrent miscarriage.
After giving birth to her son Noah in 2012, Faye and her husband Dean had 3 miscarriages. In 2015, Faye took part in the PRISM trial led by researchers at Tommy’s National Centre for Miscarriage Research. Her daughter Leila was born in 2016.
I was a broken mess and I felt like my grief was wrong because it wasn’t a real baby, like I was being dramatic, over-the-top.
Toni and her husband Matt had a miscarriage in 2015 which left Toni with PTSD. The couple live in Leicester with daughters Phoebe and Willow. This is Toni's story.
Roslyn and Paul from South Ayrshire in Scotland had an early miscarriage before getting pregnant with their first daughter Ava who is now 4 years old. They went on to lose another 3 babies before getting a referral to Tommy’s National Centre for Miscarriage Research at University Hospital in Coventry. Their second daughter, Ciara, was born in April 2019 and is now 7 months old.
Kirsty and Paul from Preston had 3 miscarriages before they were referred to the Tommy’s National Centre for Miscarriage Research at Birmingham Women’s Hospital. In January 2019, Kirsty gave birth to Alice Ivy.
Katie sadly lost two babies before falling pregnant with her third child. In this piece, Katie speaks of the heartbreak she faced, and reflects on her road to recovery.
Holly and Peter, who experienced recurrent miscarriage, had a missed miscarriage before becoming pregnant with their daughter Millie, who is now 4 years old. In 2017, they found out they were expecting again but sadly lost their baby, Sophie, at 14 weeks. After another 2 missed miscarriages, their second rainbow baby Finley arrived.
After Rebecca and Lee from Bedfordshire had 2 heart-breaking miscarriages, the learnt they were not eligible for specialist miscarriage care unless they’d lost 3 babies. Rebecca is now 16 weeks pregnant and reflects on her journey.
Danielle from Peterborough had had 3 recurrent miscarriages before being referred to the Tommy’s National Centre for Miscarriage Research. Whilst undergoing treatment, she lost another 2 babies before becoming pregnant for the sixth time. Danielle and her fiancé Ed are currently 21 weeks pregnant and their baby is due in March in 2020. This is Danielle’s story.
I felt an overwhelming rush of sadness: sadness for the loss of my first grandchild and sadness that my own baby was going through so much pain.
Anne from North Wales reflects on how she supported her daughter who had a missed miscarriage at 12 weeks.
Danielle and her husband Paul experienced a missed miscarriage before their first daughter Eva, 5, was born. They had 3 more heartbreaking losses before self-referring to Tommy’s National Centre for Miscarriage Research at Birmingham Women’s Hospital. Danielle gave birth to baby Louie in July 2019.
”If I can help just one person get through this awful experience, then it is worth it. I want people to know that they are not alone.”
Emma experienced 5 losses before her rainbow baby, Theodora, was born in December 2018.