Why doctors are so worried about pregnant people getting COVID-19

Canadians who are pregnantare at higher risk for severe illness if they get COVID-19, yet many are still hesitating to get vaccinated, experts say.

"It's terribly concerning," saidDr. Deborah Money, a professor ofobstetrics and gynecologywho specializes in reproductive infectious diseases at the University of British Columbia in Vancouver.

Money works withCanCOVID-Preg, which tracks COVID-19 in pregnancies across the country.

"Pregnant women are undervaccinated compared to the rest of the populationfor sure," she said.

Early in the pandemic, data on the potential effects of COVID-19 on pregnant people and fetuses was limited and pregnant people weren't included in clinical vaccine trials.Even the World Health Organization failed to provide clear advice on vaccination for pregnant people in the early days, which contributed to uncertainty among both pregnant people and the primary care providers trying to give them the best medical advice on vaccination.

But during the last several months,there has been growingconsensus among experts thatnot only areCOVID-19 vaccinessafe for pregnant people, but also that pregnant people are among the groups at highest risk of serious illness if they are infected with the virus and there can be consequences for their babies too.

CBC News talked toobstetrician-gynecologists, immunologists and an infectious disease expert to get the most up-to-date facts. Here's what we know.

Why are pregnant people a high-risk group?

Pregnant people who become infected with COVID-19 are more likely than non-pregnant people in their age group to become criticallyill, said Dr. Alexander Wong,an infectious diseases expert in Regina. Saskatchewan isbattling such high rates of COVID-19 hospitalization that it has had to fly critically ill patients to hospitals in other provinces.

Being fully vaccinated "dramatically" reduces that risk, Wong said.

Evidence from around the world continues to back that up, and Money said herteam is in the midst of publishing a study "showing substantially higher rates of hospitalization, ICU admission and higher rates of pre-term birth" among pregnant women in Canada who weren't vaccinated.

One key reason pregnant people are so vulnerable to infections like COVID-19, immunology experts say, is thattheir immune systems have lowered defences.

"When a person is pregnant, they're somewhat immunosuppressed because from theimmune system's perspective, the developing fetus is actuallya foreign invader," said Angela Rasmussen, a virologist at the University of Saskatchewan'sVaccine and Infectious Disease Organization (VIDO) in Saskatoon.

There are "substantial rearrangements of the immune system" during pregnancy so it doesn't start attacking the developing fetus, she said.

But vaccination triggers an effective immune response against specific threats like COVID-19, she said, so pregnant people "should definitely get vaccinated."

What about effects on the baby?

More research is showing that not only is getting vaccinated safe for both parentand fetus it likely has protective benefits after the baby is born,obstetrician-gynecologists and immunology experts told CBCNews.

Although pregnant people weren't included in clinical trials before COVID-19 vaccines were authorized, real-world data collected afterpregnant people have received the COVID-19 vaccine around the world have not raised any safety flags, they say.

In the U.S. alone, more than 160,000 pregnant womenhave been vaccinated and the Centers for Disease Control and Prevention (CDC) did not find any safety concerns, Money said.

"That is looking extraordinarily reassuring in terms of no worse outcomes and, in fact, actually a trend toward better outcomes in pregnant women versus not [vaccinated]," she said.

WATCH | B.C.'s provincial health officer debunks myths about COVID-19vaccines and pregnancy:

No risk to pregnant women from COVID vaccine: Dr. Bonnie Henry

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B.C. provincial health officer Dr. Bonnie Henry is encouraging people who are pregnant, planning to get pregnant or breastfeeding to get vaccinated against COVID-19.

Vaccinating pregnant people to protect them, as well as their babies, from virusesis "not a new idea," said Kathryn Gray, an attending physician in maternal fetal medicine at Brigham and Women's Hospital in Boston.

Influenza and Tdap (tetanus, diphtheria, pertussis) vaccines are already recommended in pregnancy as a way to ensurebabies have some antibodies against flu and whooping cough when they're born, she said.

Gray, who is also anassistantprofessor at Harvard medical school in Boston, has been researching COVID-19 in pregnancy and has foundantibodies against the virus that causes COVID-19 cross the placenta when the the parentis vaccinated, adding toincreasing evidence that immunity benefits likely extend to the baby.

"Babies are born with the antibodies that mom has during the pregnancy," said Money.

Antibodies from the vaccinehave also been found in breast milk, Money said.

"The vaccine is [an] excellent way to protect against infection and serious illness and to give the baby some protection in the first few months of life before vaccination [for them]is possible," Money said.

Not getting vaccinated puts the fetus at higher risk because people who getsick with COVID-19are more likely to deliver prematurely, Moneysaid.

Does the COVID-19 vaccine affect fertility?

No, experts say. And the spread of misinformation suggesting otherwise has been linked to many people of child-bearing age to delay getting vaccinated, they say.

"It's a complete myth," said Gray. "There is no effect on fertility of vaccination."

Not only is there no evidence of any cases that would link the vaccine to fertility, there's also no theoretical reason that couldhappen, said Dr. Jennifer Blake, CEO of theSociety of Obstetricians and Gynaecologists of Canada (SOGC) based in Ottawa.

"There is no plausible way in which this vaccine could interfere with fertility," Blake said."It has nothing to do with our ovaries and with our eggs or with sperm production."

One reason people maythink the vaccine could affect their fertilityis a study that suggested some people who had received itmay have had temporary changes in their menstrual cycle for a month or two. However it's not clear if there was a direct link, said Money.

Even if there was, "that doesn't translate to infertility by any stretch," she said.

"It's really worrisome because all this mythology about fertility and all this misinformation has meant that pregnant women are some of the lowest vaccinated even though they should be the most vaccinated," said Dawn Bowdish, an immunology professor at Hamilton'sMcMaster University in Hamilton who is conducting a study onpregnant people and COVID-19.

What about miscarriages?

There is no evidence of any link between vaccines and miscarriages, all threeobstetrician-gynecologistsinterviewed said.

When is the best time for a pregnant personto get vaccinated?

The COVID-19 vaccine is safe before and during any point in the pregnancy, as well as while breastfeeding, the experts said, noting that the best time to get vaccinated is as soon as possible.

If pregnant people are a high-risk group, should they get booster shots?

In the U.S., the CDC says people who are pregnant may receive a boosterbecause of their risk of "severe infection." The timing of an mRNA vaccine booster is at least six months after the second dose of vaccine.

In Canada, the National Advisory Committee on Immunization (NACI) has not yet recommended boosters for pregnant people.

What are the COVID-19 vaccination rates among pregnant people?

According to the CDC, about 35 per cent of pregnant people in the U.S. are fully vaccinated, compared to about 68 per cent of the general population.

It's difficult to get national data on vaccination rates among pregnant people in Canada,Money said, and there's a lot of variability between theprovinces and territories. The most readily available data is in Ontario. According to ICES (formerly known as the Institute forClinical Evaluative Sciences), about 60 per cent of pregnant people in Ontario are fully vaccinated, compared to around 80 per cent of the eligible population in the province.