Almost a fifth of the most critically ill coronavirus patients in England in recent months were unvaccinated pregnant women.

NHS England said that, between July 1 and September 30, 17 per cent of Covid patients receiving treatment through a special lung-bypass machine were mothers-to-be who had not had their first dose of a Covid-19 vaccine.

The organisation said data also showed that pregnant women accounted for 32 per cent of all females aged between 16 and 49 in intensive care on extracorporeal membrane oxygenation (ECMO) – used when a patient’s lungs are so damaged by Covid that a ventilator cannot maintain oxygen levels.

NHS England said this figure has risen from 6 per cent at the beginning of the pandemic in March 2020.

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

But the National Childbirth Trust (NCT) said the statistics are a “damning indictment of the lack of attention given to this vulnerable group as restrictions have eased”.

NHS England said data from more than 100,000 Covid vaccinations in pregnancy in England and Scotland, and a further 160,000 in the US, show there has been no subsequent harm to the foetus or infant.

Dr Edward Morris, president of the Royal College of Obstetricians and Gynaecologists, said medics understand women’s concerns but want to offer reassurance that the vaccine is safe.

He said the “disproportionate” number of unvaccinated pregnant women in intensive care shows there is a “significant risk of severe illness from Covid-19 in pregnancy”.

He said: “We are urgently calling for all pregnant women to come forward for their vaccinations.

“There is robust evidence showing that the vaccine is the most effective way to protect both mother and baby against the possibility of severe illness from Covid-19.”

Public Health England data shows more than 81,000 pregnant women have received the first dose of a Covid vaccine, and around 65,000 have received their second dose, NHS England said.