More than 99% of pregnant women admitted to hospital with Covid-19 are unvaccinated – with the Delta variant of coronavirus posing a significantly greater risk of severe disease, scientists have said.

Researchers at Oxford University have described their findings as “concerning”, saying that one in 10 pregnant women admitted to hospital with symptoms of Covid-19 often require intensive care.

In a study, published in an online server called medRxiv, the scientists said that vaccinations are able to offer effective protection from the risk of becoming severely ill from Covid-19, with far fewer numbers from vaccinated groups in hospital compared with those who have not had the jab.

I cannot emphasise more strongly how important it is for pregnant women to get vaccinated in order to protect both them and their baby

Marian Knight, professor of maternal and child population health at the Nuffield Department of Population Health, University of Oxford, and chief investigator of the study, said: “It is extremely good news that so few vaccinated pregnant women have been admitted to hospital with Covid-19.

“However, it is very concerning that admissions of pregnant women to hospital with Covid-19 are increasing and that pregnant women appear to be more severely affected by the Delta variant of the disease.

“Around 200 pregnant women were admitted to hospital with Covid-19 last week.

“I cannot emphasise more strongly how important it is for pregnant women to get vaccinated in order to protect both them and their baby.”

For the study, the researchers looked at the data from the UK Obstetric Surveillance System (UKOSS), involving all pregnant women in the UK admitted to hospital with symptoms of Covid-19 from the beginning of the pandemic to up to July 11 2021.

Other studies have shown that women who have received a vaccine pass on antibodies to their babies, so the benefits of vaccination to both pregnant women and their babies are clear

They found that 3,371 pregnant women were admitted to hospital with symptoms of the disease.

The researchers also discovered that the severity of women’s illness appeared to have become worse over the course of the pandemic – with 24% of women admitted in the first wave having moderate or severe disease, compared with 36% with the Alpha variant and 45% with the Delta variant.

The scientists also looked at the vaccination data collected since February 1 2021 and found that of the 742 women admitted since that date, only four have received a single dose of vaccine and none have received both doses.

Nicola Vousden, registrar in public health at the Nuffield Department of Population Health and the first author of the study, said: “This study shows that very few pregnant women are admitted to hospital with Covid-19 after they have received a vaccine.

“Other studies have shown that women who have received a vaccine pass on antibodies to their babies, so the benefits of vaccination to both pregnant women and their babies are clear.”

We want to reassure pregnant women that Covid-19 vaccines are the safest and best way to protect you and your baby from severe illness and premature birth

The Royal College of Obstetricians and Gynaecologists (RCOG) and the Royal College of Midwives recommend that women who are pregnant or considering pregnancy get their Covid-19 vaccine as soon as possible.

England’s chief midwife Jacqueline Dunkley-Bent said: “Vaccines save lives, and this is another stark reminder that the Covid-19 jab can keep you, your baby and your loved ones safe and out of hospital.”

Dr Edward Morris, president of the RCOG, said: “Every day our members are seeing very sick pregnant women with Covid-19 in hospital and the majority are unvaccinated.

“We want to reassure pregnant women that Covid-19 vaccines are the safest and best way to protect you and your baby from severe illness and premature birth.”