“…In that study on patients with normal pulmonary artery pressure, the ejection flow reached a peak during midsystole; in contrast, in patients with pulmonary hypertension the ejection flow peaked sooner (shorter acceleration time), which translates into lower PATET values in the setting of a high impedance to flow, and vice versa. (2) As described by Rasanen et al [9] , the pulmonary arterial impedance decreases as the gestational age advances, and we hypothesized that this could result from continued pulmonary angiogenesis, a larger vascular lumen, increased vessel wall elasticity, and/or an increasing concentration of surfactant during the late third trimester, all of which are related to lung maturation [10,11] .…”