STRIDER (NZAus): A randomised placebo-controlled trial of a new therapy (sildenafil) to help growth in severely growth restricted fetuses at very early gestations.

Intrauterine growth restriction (IUGR) describes conditions where fetuses are smaller than expected for their gestational age. This puts the fetus at risk of death, hypoxia and preterm birth. If IUGR occurs early in pregnancy (i.e before 28 weeks gestation) survival rates are only 70% and survival free of major handicap (intact survival) is much lower at 20%. Current management involves intensive fetal surveillance and delivery when there is evidence of serious compromise (to avoid death in utero) but this leads to the consequent risks of prematurity. There is no known treatment for IUGR. This is a double blind randomised placebo controlled trial of Sildenafil, a nitric oxide donor drug, that has the potential to vasodilate uteroplacental vessels improving placental function. It may represent a novel therapy for IUGR. It has been used in pregnancy without adverse events and in a small case-control study it improved daily fetal growth velocity. Women with severe early onset IUGR will be invited to take part in the study at MFM units across NZ and Australia. This study will demonstrate if Sildenafil improves fetal growth, the results will be used in collaboration with other similar studies planned worldwide to demonstrate if Sildenafil improves rates of survival free of major handicap. This trial incorporates the STRIDER NZAus Childhood Outcome Study: a follow up assessment of all surviving children at 2-3 years’ corrected age to determine whether any benefit (or harm) seen in the newborn as a consequence of antenatal sildenafil therapy is sustained, or develops, through childhood.