Placental histopathology in early-onset fetal growth restriction with use of sildenafil, a secondary analysis of the Dutch STRIDER study.

Objectives: Placental pathology lesions are common in early-onset fetal growth restriction (eoFGR). Therapeutic interventions to improve eoFGR outcomes are needed. In the international STRIDER trials (Sildenafil Therapy In Dismal prognosis Early-onset intrauterine growth Restriction) sildenafil didn't improve perinatal outcomes of eoFGR. We aimed to study the underlying placental pathology in the Dutch STRIDER trial and the effects of sildenafil on placental histopathology by describing the associations with sildenafil treatment, placental-dysfunction serum biomarkers and markers of oxidative stress.

Methods: The Dutch STRIDER trial was a randomized controlled trial of sildenafil versus placebo in 216 singleton pregnancies complicated by eoFGR, included between 20+0- and 29+6-weeks' gestation. In 158 cases, placental histology was available. Lesions were classified independently by three perinatal pathologists blinded for clinical data, according to the international criteria of the Amsterdam Placental Workshop Group Consensus Statement. Blood samples taken at inclusion were analyzed for free thiols (FT), placental growth factor (PlGF) and soluble FMS-like tyrosine kinase-1 (sFlt-1, n = 85).

Results: The 'big four' placental lesions (maternal and fetal vascular malperfusion, and chronic or acute inflammatory lesions) were equally distributed in both groups. However, massive perivillous fibrin deposition (MPFD) and chronic histiocytic intervillositis (CHIV) were less common in the sildenafil-treated group compared to the placebo-treated group (p = 0.026 and p = 0.043). FT, PlGF and sFlt-1 at inclusion were not discriminative for placental lesions.

Conclusions: Sildenafil had no effect on common placental lesions. The lower incidence of MPFD and CHIV after sildenafil exposure merits more research on the interaction between sildenafil and the immune system.