A Blood pressure = stroke volume X heart rate.
B Left-to-right shunting across the duct is normal in the fetus.
C The fetal heart does not start pumping blood until 18–20 weeks, because the placenta performs this function.
D Contractility of the heart is independent of preload and afterload.
E The ductus arteriosus can be kept open by the use of ibuprofen or indomethacin, but these have some side effects.