It can occur during pregnancy and up to a year after the baby is born.

Britney Spears appears to have announced she's pregnant with her third child in an Instagram post.

The singer, 40, describes gaining weight and thinking she was "food pregnant" after a trip to Maui, but after taking a pregnancy test she says she discovered she was "having a baby."

The mum-of-two posted: "It's hard because when I was pregnant I had perinatal depression... I have to say it is absolutely horrible...

"Women didn't talk about it back then... Some people considered it dangerous if a woman complained like that with a baby inside her... But now women talk about it every day."

Spears became engaged to fitness model partner Sam Asghari in September 2021, and a 13-year conservatorship came to an end the following November.

She has two children, Sean Preston, 16, and Jayden James, 15, with ex-husband Kevin Federline, and testified in court that the conservatorship prevented her from having more children.

Following Spears' announcement, Asghari posted on Instagram: "Marriage and kids are a natural part of a strong relationship filled with love and respect. Fatherhood is something I have always looked forward to and I don't take lightly. It is the most important job I will ever do."

According to a review by the Centre for Mental Health, between 10 and 20% of women experience perinatal mental illness.

Here's everything you need to know.

What is it?

While postnatal depression occurs during the first year after giving birth, "perinatal depression can occur at any point between becoming pregnant and up to one year after your child is born," explains Cheryl Lythgoe, matron at Benenden Health (benenden.co.uk), although she says there is evidence that "parents can suffer for up to three years after birth".

She says: "Feeling anxious or tearful in the first few days after birth is common. It's often called the 'baby blues' and doesn't tend to last more than a couple of weeks. If symptoms last longer - or start later - it could be postnatal depression."

What are the symptoms?

There are a wide range of symptoms of perinatal ill health, says Lythgoe, citing "anxiety, feeling low and not enjoying your pregnancy, a loss of self confidence, avoiding socialising, obsessive compulsive disorder and a lack of energy" as some of the most common.

She says mixed emotions are common for parents - because "pregnancy and birth are big milestones" - but "if you find the way you feel starts to impact your life every day, you could be suffering from perinatal mental illness".

The charity Mind list feeling restless, agitated or irritable, guilty, worthless, empty, numb, tearful, unable to relate to other people, finding no pleasure in life, a sense of unreality, hopeless and despairing, hostile or indifferent to your partner, hostile or indifferent to your baby, and suicidal feelings, as symptoms too.

Are there any misconceptions around perinatal depression?

"It's not just new mums who suffer," Lythgoe suggests. "Dads can be affected by perinatal depression too, so it's worth being aware and watching out for the signs."

How can you seek help?

Lythgoe's top piece of advice for anyone who thinks they might be struggling with perinatal depression is to be "open and honest - not only with yourself, but also with your family and clinical care team, as looking after your mental wellbeing is just as important as looking after your physical health".

Speak to your GP if you have any concerns, or you could get in contact with perinatal mental health support charity PANDAS (pandasfoundation.org.uk) either via their website or their free helpline on 0808 1961 776.

"During the perinatal period, using psychological therapies is a great way to support mental wellbeing," says Lythgoe. Anyone with existing mental health concerns may be at a higher risk when they fall pregnant, and in this case she recommends pre-conception counselling and support.

Lythgoe advises: "As well as getting help from the professionals, there are a few things you can try to help ease your symptoms, including talking to your family and friends about your feelings, accepting help, enjoying some 'me time', exercising, eating healthily whilst not missing meals, and avoiding alcohol and drugs."

Anyone with suicidal feelings can contact Samaritans 24-hours a day for free on 116 123.