The rise in infections is thought to have been fuelled by a combination of vaccine hesitancy and the relaxation of restrictions.

       Only around one in 12 — 51,724 — expectant mothers are reported to have had at least one dose of vaccine.

       Reports claim that in mid-July 160 women were admitted to hospital with the virus – compared with just 28 in the last week of May.

       In the first three days of last week, 125 were admitted.

       Professor Marian Knight, the chief investigator of a study of pregnant women admitted to hospital with Covid-19, urged expectant mothers to get vaccinated.

       She said: "No pregnant women who have received both doses of vaccine have been admitted to hospital since the vaccination programme began."

       She said vaccination was "the best way" to protect against Covid-19 for both mother and baby.