Women who suffer from COVID-19 during pregnancy appear at greater risk of preterm births and stillbirths, according to a federal report co-written by a HealthPartners researcher.

The study published Wednesday by the U.S. Centers for Disease Control and Prevention was based on 105 pregnant women with COVID-19 who were hospitalized this spring. Among the 93 with birth outcomes by the end of July, 15% suffered preterm births and 3% had stillbirths.

Both rates were higher than in a comparison group of pregnant women and may have to do with the pressure that COVID-19 places on the vascular system and with the overreaction by the immune system, said Dr. Elyse Kharbanda, a maternal and child health researcher at the HealthPartners Institute in Bloomington.

"When you have a symptomatic infection, it induces a very strong inflammatory response and can lead to vascular complications," she said. "And these vascular complications affect blood flow to the developing fetus, they affect the placenta, so that is likely contributing."

HealthPartners was one of eight obstetric providers contributing to the study, which also found more hospitalizations for COVID-19 among women who had gestational diabetes or obesity before pregnancy.

The CDC lists pregnancy as a possible risk for severe COVID-19, an infectious disease caused by exposure to a novel coronavirus. Cancer, kidney disease, chronic obstructive pulmonary disease, weakened immune systems, obesity, serious heart conditions, sickle cell disease and diabetes are considered high risk conditions for severe COVID-19.

More than nine in 10 deaths in Minnesota have involved people 70 or older or with underlying health conditions.

The state reported seven COVID-19 deaths and 513 lab-confirmed infections on Wednesday, bringing the totals in the pandemic to 1,933 deaths and 85,813 infections.

Hospitalizations remained near two-month lows on Wednesday, with 244 COVID-19 patients being admitted to hospitals and 136 needing intensive care.

State death records show a 49-year-old woman was pregnant when she died of COVID-19 in July, and women aged 43 and 35 were pregnant within 42 days of their deaths earlier in the year.

In total, 52 of the state's COVID-19 deaths involved people younger than 50.

State infectious disease director Kris Ehresmann said she was "not surprised" by the CDC's findings of COVID-19 pregnancy risks, even though the state's own data showed lower rates of poor outcomes.

Roughly 1,000 COVID-19 cases in Minnesota have involved pregnant women, who are often identified through routine screening during obstetric and hospital visits. One in five were asymptomatic.

An analysis of outcomes for 246 pregnant women with COVID-19 in Minnesota showed 256 live births, one pregnancy termination, two stillbirths (fetal death at 20 weeks or more gestation), and two miscarriages (fetal deaths before 20 weeks gestation).

Of the 256 children, 36 were admitted to neonatal intensive care for complications — including 21 born prematurely.

In the CDC study, the stillbirth prevalence for women with COVID-19 was four times greater than the 0.6% rate in a comparative group of pregnant women. However, that was based on three stillbirths in the study group — a small number that calls for caution in interpreting the results, Kharbanda said.

Kharbanda said other studies have examined hospitalization rates of pregnant women with COVID-19, but the CDC study was novel for determining whether they went to hospitals for COVID-19 or pregnancy concerns — and how many had asymptomatic infections that they didn't know about until they were tested as a precaution.

Among the 103 women hospitalized, 49 sought pregnancy care and had cases detected through routine testing.

The report encouraged obstetricians and family doctors to emphasize COVID-19 prevention strategies, including mask-wearing and maintaining social distancing from others during pregnancy.

Jeremy Olson • 612-673-7744