Plasma and amniotic fluid concentrations of nitric oxide: Effects on uterine artery and placental vasculature in women who underwent voluntary pregnancy termination and in women with missed and threatened abortion. A pilot study

•First trimester miscarriage is a multifactorial event. Various angiogenic factors have been proposed as possible early markers of non-viable pregnancies. We aim to evaluate the systemic nitric oxide (NO) production in healthy early pregnancy and its possible role in first trimester miscarriage, comparing its concentration in women who underwent voluntary pregnancy termination, women with missed and threatened abortion.•In our study we observed that amniotic fluid NO concentration is higher in early viable pregnancies (elective termination of pregnancy) than in the missed abortions. Moreover, amniotic fluid NO concentrations are positively related to Doppler 3D indices of vascularization and blood flow within the placenta.•Thus, low levels of amniotic fluid NO concentration may represent a specific reduced stimulus to angiogenesis with possible subsequent inefficient placentation, resulting in first trimester miscarriage.