REN and COVID-19: A key complication of pregnancy seen in patients with a COVID-19 infection was the increased risk of developing preeclampsia. The angiotensin-converting enzyme 2 (ACE2) receptor is an important part of the renin-angiotensin system, which has been implicated in the control of blood flow and also is a key receptor in the pathogenesis of the multitude of symptoms of COVID-19.