Contact Us

About the STRIDER Trial

EudraCT number: 2013-005398-32


The STRIDER trial will determine whether oral sildenafil improves outcomes in pregnancies complicated by severe early-onset intrauterine growth restriction without increasing risks to the mother.



Fetal growth restriction, commonly called intrauterine growth restriction (IUGR), occurs when the placenta has failed to develop correctly. In most cases this has happened in the early stages of pregnancy but is usually only recognised when the baby is found to be small on ultrasound around 20 weeks.


The earlier IUGR is recognised the more severe it usually is. It is babies like this that the STRIDER trial is aiming to help.


There is currently no treatment for IUGR.

The doctors and midwives looking after IUGR babies will carefully monitor the baby to try to gain as much time in the womb as possible but still to deliver before the baby becomes too sick.

Survival for IUGR babies depends on the birthweight and the number of weeks (gestation) they are at birth. Therefore, a medication that can improve weight or prolong the time to deliver could have significant advantages for these very sick babies.


IUGR is linked with:

• stillbirth (the baby dying before birth)
• the need to deliver the baby before the end of pregnancy (preterm delivery)
• serious health problems for the baby soon after birth, including death
• health problems as the baby grows into a child and an adult


Sildenafil, commonly called VIAGRA, causes blood vessels to relax and has been used for many years for the treatment of male erectile problems. Sildenafil may also be able to cause the blood vessels supplying the placenta to relax improving the blood supply to the placenta in IUGR pregnancies. Improving the blood supply to the placenta should improve the growth and well-being of the IUGR baby.


We expect that babies treated with sildenafil will be delivered one week later compared to those treated with placebo. This one week increase is clinically very important.


Sildenafil has been used in a small number of pregnancies before, and appears to be safe. However, we will closely monitor the safety of this treatment throughout the STRIDER study to ensure that no harm is caused.


Research plan

Women less than 30 weeks of pregnancy with an IUGR baby will be invited to participate in the STRIDER study. 

Women who agree to take part will be given sildenafil or placebo (sugar pills) tablets until delivery, or 32 weeks of pregnancy, whichever comes first.

We will collect information from ultrasound scans, blood tests, blood pressure and tests on the placenta.
The STRIDER study will recruit for 2 years.



The STRIDER trial is funded by a National Institute for Health Research ‘Efficacy and Mechanism Evaluation’ grant. This research is being organised by the Centre for Women’s Health Research at the University of Liverpool.