Michelle Barron, senior director of infection prevention and control at UCHealth [and professor of medicine at CU School of Medicine], said about half of the system’s female patients between the ages of 18 and 44 have been pregnant so far this year. During the 2019-2020 flu season — the last normal one before the pandemic — only about 17% were, which is more typical, she said. “Seventeen percent to 50% is a huge jump, based on historically what we’ve seen,” she said.