England’s chief midwife has written to GPs and fellow midwives across the country urging them to encourage expectant mothers to get a coronavirus jab after research showed the vast majority of pregnant women admitted to hospital with Covid-19 are unvaccinated.

Jacqueline Dunkley-Bent, chief midwifery officer for England, said the figures are “another stark reminder” that the jabs can keep women and their babies safe from coronavirus and out of hospital.

Scientists said more than 99% of pregnant women admitted to hospital with the virus have not been vaccinated – with the Delta variant of coronavirus posing a significantly greater risk of severe disease.

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.

Ms 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.”

She added: “I am calling on pregnant women to take action to protect themselves and their babies and on my fellow midwives to ensure they have the information they need to do so.”

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.

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.”

She said pregnant women can be “reassured” about the safety of the vaccine and that antibodies will be passed to their babies.

She told BBC Radio 4’s Today Programme: “We need to emphasise the benefits, not only to them but we know that antibodies are passed on to their babies as well, so it’s really important not just to prevent illness in you as a pregnant woman, but also to prevent the consequences of illness for your 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.

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.”

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.”

NHS England has advised that any pregnant women with questions or concerns about the vaccine can speak to their GP, midwife or obstetrician to get more information and advice and can book an appointment to get their jab on the NHS National Booking Service website or call 119 between 7am and 11pm.