Figure 1.

(a–d) Measurement of spiral artery luminal diameter using the B‐flow/STIC M‐mode technique in an untreated baboon on day 60 of gestation: (a) a spiral artery was identified in the placental bed (yellow shaded area) using power Doppler; (b) B‐flow was activated and the spiral artery was demonstrated at the same anatomical location; (c) a 4D‐STIC block was acquired and the spiral artery was visualized in the three orthogonal planes; (d) during post‐processing, M‐mode was activated at the z‐axis and the spiral artery luminal diameter was measured perpendicular (red arrow) to the vessel lumen. Fetal heart rate was measured each time to confirm that the blood vessel was a maternal vessel. (e,f) Representative B‐flow/STIC M‐mode measurement of spiral artery luminal diameter during the cardiac cycle (1: diastole, 2: systole) in an untreated baboon (e) and in a baboon with spiral artery remodeling impairment following estradiol treatment (f).