This study examined whether the type-5 phosphodiesterase inhibitor sildenafil citrate (Viagra; Pfizer, New York, NY) could increase uterine blood flow in intrauterine growth restriction (IUGR), thereby improving fetal oxygenation and well being.Study Design
In fetal sheep, we induced IUGR at 105-110 days (0.7 gestation) using single umbilical artery ligation (SUAL). In SUAL and control animals, we measured uterine blood flow (UBF) and blood gases before and after sildenafil administration.Results
SUAL fetuses were hypoxemic compared with controls. Following sildenafil, UBF was significantly decreased in both SUAL and control ewes for ˜40 minutes. In response to sildenafil, pO2 was decreased in SUAL and control fetuses and both groups displayed significant hypotension and tachycardia. At postmortem SUAL fetal body weight was significantly reduced by 23% compared with controls.Conclusion
Sildenafil does not improve UBF or fetal well being in SUAL-induced IUGR pregnancies and should be used with caution in IUGR and healthy pregnancies because of its detrimental effects on uteroplacental perfusion and on the fetus.