STRIDER stands for Sildenafil TheRapy In Dismal prognosis Early onset intrauterine growth Restriction. The STRIDER NZAus trial aims to determine whether sildenafil therapy can improve the growth of babies affected by severe, early-onset growth restriction while they are still in the womb.

The term intrauterine growth restriction (IUGR), also known as fetal growth restriction (FGR) describes a baby that is failing to grow to its full potential whilst still inside the womb. It affects up to 10% of all pregnancies. There is currently no effective treatment that can be given before birth. It may result in stillbirth or the need for very early birth; being born too small and too early may cause a number of short and long-term health problems.

The primary outcome of this study is the proportion of pregnancies with an increase in the rate of fetal growth (measured by the baby’s abdominal circumference growth on ultrasound). If fetal growth and wellbeing improves it may be possible to delay delivery leading to higher survival rates and a reduction in complications that lead to life-time handicap and disease.

The STRIDER NZAus trial forms part of an international consortium of trials designed to assess the potential of sildenafil therapy for severe, early onset fetal growth restriction. Each of the STRIDER Consortium trials has been independently funded by national public funding bodies and independently executed and will be published as an individual trial.

However, prospectively planned individual participant data and trial level meta-analyses will allow assessment of meaningful clinical outcomes including infant survival to primary hospital discharge without evidence of serious adverse neonatal outcome and survival free of neurosensory impairment at 2-3 years corrected age.

How the STRIDER NZAus trial was carried out

122 women with a singleton pregnancy between 22 to 30 weeks gestation with severe fetal growth restriction were randomised between February 2014 and March 2017 at 13 different maternal fetal medicine units across New Zealand and Australia.

The women were randomly assigned to either sildenafil or a visually identical placebo. These tablets were taken three times daily from study entry until 32 weeks gestation, birth or in-utero death (whichever occurred first). Participants were monitored by their local maternal fetal medicine team and had ultrasound scans at randomisation, 48 hours, day 5, day 10, day 14 and weekly thereafter.

Health outcomes were collected until the time both mother and baby were discharged from hospital after birth.

Consent to contact families at 2-3 years of age was collected and this follow-up is through the STRIDER NZAus Childhood Outcome Study.

The results of the STRIDER NZAus trial were presented at the PSANZ Annual Scientific Congress in March 2018.

Key publications

Ganzevoort W, Alfirevic Z, von Dadelszen P, et al. STRIDER: Sildenafil Therapy In Dismal prognosis Early-onset intrauterine growth Restriction--a protocol for a systematic review with individual participant data and aggregate data meta-analysis and trial sequential analysis. Systematic reviews 2014; 3: 23.

Pels A, Kenny LC, Alfirevic Z, Baker PN, von Dadelszen P, Gluud C, Kariya CT, Mol BW, Papageorghiou AT, van Wassenaer-Leemhuis AG, Ganzevoort W, Groom KM; international STRIDER Consortium. STRIDER (Sildenafil TheRapy in dismal prognosis early onset fetal growth restriction): an international consortium of randomised placebo-controlled trials. BMC Pregnancy Childbirth 2017; 17: 440.

Ganzevoort, W; Gluud, C; LIM, K; Mol, B.W; Groom, K,M. The STRIDER trials: ongoing research. The Lancet Child and Adolescent Health 2018 2 (3):e3..

Groom, K.M; Ganzevoort, W; ALFIREVIC, Z; LIM, K; PAPAGEORGHIOU, A.T. Clinicians should stop prescribing sildenafil for fetal growth restriction (FGR): comment from the STRIDER Consortium. Ultrasound Obstet Gynecol 2018; 52 (3):295-296. Doi:10.1002/uog.19186.