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

INTERVENTION: Sildenafil 25mg three times a day as an oral tablet from randomisation until delivery (or 32 weeks gestation, whichever occurs first). CONDITION: Severe early onset fetal growth restriction PRIMARY OUTCOME: The proportion of pregnancies with increased abdominal circumference (AC) growth velocity post treatment compared to pretreatment. SECONDARY OUTCOME: Changes in uteroplacental, umbilical and fetal Doppler waveform studies. Mean absolute change in abdominal circumference (mm) per day Mean birthweight and mean birthweight centile Measures of neonatal outcome; live‐births, survival to hospital discharge, major morbidity including chronic lung disease requiring ambulatory oxygen therapy on hospital discharge, intraventricular haemorrhage grade 3‐4, >grade 2 retinopathy of prematurity, necrotising enterocolitis, number of doses of surfactant, ventilator days, supplemental oxygen days and number of days to full feeds Primary outcome of the childhood follow up assessment (STRIDER NZAus Childhood Follow Up Study): Survival free of neurosensory impairment at 2.5 years’ corrected age, defined by absence of cerebral palsy, deafness, blindness, cognitive delay (Bayley‐III composite score cognition or language >1 SD below test mean) and motor delay (Bayley‐III composite motor score >1 SD below test mean). Randomisation‐to‐delivery interval INCLUSION CRITERIA: 1. Singleton pregnancy. 2a. At 22+0 weeks to 27+6 weeks: AC measure less than or equal to 3 percentile for gestational age; OR 2b. At 28+0 weeks to 29+6 weeks ultrasound estimate of fetal weight (EFW) <700grams.