Principal Investigator –Professor Louise Kenny (Cork University Maternity Hospital)

The STRIDER study is a randomised double blind, placebo-controlled clinical trial to quantify the effects of administration of sildenafil on pregnancy outcome in severe early-onset intrauterine growth restriction (IUGR).

IUGR is when an unborn baby is smaller than it should be and is not growing at a normal rate inside the womb. Currently, there is no antenatal treatment for severe early-onset IUGR. Management strategies involve intensive fetal surveillance with elective delivery performed in order to rescue the baby from an adverse environment within the womb. At gestational ages <28weeks, pre-term delivery is associated with significant perinatal morbidity and mortality. Intact survival is less than 25% for an infant weighing 600g born at 25 completed weeks’ gestation, and is still only approximately 50% up to 28 weeks’ gestation. The key determinants of death and morbidity in severe early-onset IUGR are gestational age at birth and birth weight. Importantly, an increase in neonatal survival of 2% is reported for each additional day in the womb.

In this trial 130 women with affected pregnancies will be recruited and randomised to receive either sildenafil or placebo. Previous studies indicate Sildenafil expands the blood vessels leading to increased blood and oxygen supply to the placenta and fetus and also contributes to an increase in birth weight of sildenafil treated newborns.

The current absence of treatments for this condition alongside the limited evidence means there are opportunities to conduct randomized control trials (RCT) using sildenafil. Research has identified any intervention that could prolong gestational age could have significant beneficial effects on survival and disability prevention. Therefore, the primary aim of Strider clinical trial is the use of sildenafil to increase birth weight through prolonging of gestational age.