Carrie Johnson admitted to hospital after postpartum illness

Carrie Johnson has shared a warning for breastfeeding mums after revealing she was hospitalised with severe dehydration. The 37-year-old welcomed her fourth child with former prime minister Boris Johnson, 61, last month. Poppy Eliza Josephine Johnson - nicknamed Pops or Pop Tart - was born on 21 May.

Sharing a photo of herself and the baby in a hospital bed, Ms Johnson wrote on Instagram: "Being hospitalised for two nights for severe dehydration was not on my postpartum bingo card. Breastfeeding mums make sure you eat and drink enough in this heat. Especially if your babe is cluster feeding."

Cluster feeding, when a baby feeds more frequently, is common in the first three to four months after birth, particularly during growth spurts.

It can lead to maternal dehydration if the mum is not consuming enough to replenish fluids. The NHS advises that babies may want to feed more frequently during hot weather, when risk of dehydration is also higher.

Ms Johnson added: "This week has honestly been brutal. Mastitis (me), reflux (her), dehydration (me). What a pair we are!

"But thank you for all the kindest messages, especially all the brilliant advice on reflux.

"Really appreciate it and made me feel way less alone going thru [sic] it all. And as ever, thanks to our amazing NHS."

Mastitis is a painful inflammation in the breast tissue often associated with breastfeeding. Reflux occurs when the stomach contents comes back up into the oesophagus.

It is very common in babies and usually gets better as they grow.

Poppy joins the couple's three other children, sons Wilfred, five, and one-year-old Frank, and daughter Romy, three.

Announcing the latest arrival last month, Ms Johnson wrote: "I can't believe how pretty and tiny you are. Feel so incredibly lucky. We are all totally smitten.

"Not sure I've slept a minute since you were born as can't stop looking at how completely lovely you are."

Mrs Johnson, a former communications director for the Conservative Party, also hinted that their fourth child would be their last, describing Poppy as a "final gang member".