This is a G3P2 35-year-old patient seen at 32 weeks 3 days.
The father of the fetus was born with a bicuspid aortic valve and had surgery for this. An episode of tachycardia was noted during the ultrasound exam with a fetal heart rate of 214 bpm. A thin "lace-like" membrane is seen in the right atrium. Findings were thought to most likely represent a remnant of the septum spurium known as a Chiari net. The remainder of the cardiac anatomy appears normal at this time.
Image 1: The big arrow shows the typical appearance of Chiari net, the small one shows the flap valve of the foramen ovale.