Kate makes her first public appearance since announcing her third pregnancy

Kate, the Duchess of Cambridge has stepped out in public for the first time since announcing her third pregnancy.

Kate, 35, returned to her royal duties by making an appearance at an reception held at Buckingham Palace for World Mental Health Day, where mental health workers were invited to mark the occasion with the family.

The mum-of-two showed off just a hint of a bump beneath her £795 blue lace dress, which was designed by Temperley London, as she chatted with the assembled crowds alongside husband Prince William.

Since confirming that she was expecting again back in September, Kate has been suffering with hyperemesis gravidarum, a severe form of morning sickness which she's battled through all three pregnancies, and most recently, led her to miss several engagements, as well as her son Prince George's first day of school.

At the event, an aide reportedly confirmed that the condition is ongoing, but 'Kate was determined to attend the event because the cause is close to her heart'.

'The duchess' condition is improving but she is still suffering from hyperemesis gravidarum. She is delighted to be able to be here tonight,' they explained.

Dr Nicola Byrom, of charity Student Minds, commended Kate on her dedication to attendance, commenting: 'She's amazing. What a fighter that she's here.'

It is thought that Kate is nearing the end of her first trimester, although Kensington Palace have not yet formally confirmed a due date.

Shortly after the pregnancy news was revealed, Prince William sparked rumours that his wife could already be three months along, as he remarked that it had been an 'anxious time so far', but they could start celebrating soon.

'There's not much sleep going on at the moment,' he admitted at the time, but added that the new addition to the Cambridge family was 'very good news.'