- Coronavirus pandemic
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Carrie Johnson has said she is "feeling great" after having her second Covid jab, as she encouraged other pregnant women to get the vaccine.
The prime minister's wife said she understood people's anxieties but that the evidence was "reassuring".
Mrs Johnson said there was no increased risk of miscarriage – adding she had been "definitely concerned" about that.
Announcing her pregnancy last month, she also revealed she had a miscarriage earlier this year.
Her post on Instagram about getting the jab comes after England's chief midwife urged pregnant women to be vaccinated as soon as possible.
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When the UK's vaccination programme started, the original advice for pregnant women was to avoid the jab for the time being – because doctors are extremely cautious about what they recommend during pregnancy.
But when safety data became available, the advice changed to encourage pregnant women to have the vaccine, especially because contracting Covid can be dangerous for expectant mothers.
The 33-year-old, who married Boris Johnson in May and is mother to one-year-old Wilfred, wrote: "Just had my second jab and feeling great!
"I know there are lots of pregnant women who are anxious about getting their Covid vaccine but the evidence is incredibly reassuring."
image sourceRebecca Fulton/Downing Street/PA Wire image captionBoris Johnson and Carrie in the garden of 10 Downing Street after their wedding earlier this year
She added: "Most importantly, the data shows there is no increased risk of miscarriage, something I was definitely concerned about."
Mrs Johnson had a miscarriage in early 2021, which she said left her "heartbroken". She said she felt "blessed to be pregnant again" but "felt like a bag of nerves".
In Saturday's Instagram post, accompanied by a selfie in which she is wearing a sticker showing she has had her vaccine, Mrs Johnson said nearly 200,000 pregnant women in the UK and US had now had a Pfizer or Moderna vaccine "without safety concerns".
"The Royal College of Midwives has said that expectant mothers are at greater risk of serious illness if they get Covid so being vaccinated really is the best way to keep you and your baby safe," she wrote.
image sourceGetty Imagesimage captionCarrie, seen here with First Lady Jill Biden at the G7 summit in Cornwall, gave birth to son Wilfred in April 2020
Since mid-April 2021, mothers-to-be have been offered the Pfizer or Moderna coronavirus jab, with the second dose recommended eight weeks after the first.
But figures out last month, from estimates based on GP records and Public Health England data, suggested hundreds of thousands had not had the jab.
Data looking at pregnant women admitted to English hospitals up to July showed that, in the previous three months, 171 pregnant women had been admitted to hospital with Covid symptoms – 98% were unvaccinated, and three of them had received a single dose of the vaccine.
If you or someone you know has been affected by miscarriage or other pregnancy-related issues, support can be found through BBC Action Line.