A smear test detects abnormal cells on the cervix, which is the entrance to the uterus from the vagina.
Removing these cells can prevent cervical cancer.
Most test results come back clear, however, one in 20 women show abnormal changes to the cells of their cervix.
In some cases, these need to be removed or can become cancerous.
Being screened regularly means any abnormal changes in the cells of the cervix can be identified at an early stage and, if necessary, treated to stop cancer developing (stock)
Cervical cancer most commonly affects sexually-active women aged between 30 and 45.
In the UK, the NHS Cervical Screening Programme invites women aged 25-to-49 for a smear every three years, those aged 50 to 60 every five years, and women over 65 if they have not been screened since 50 or have previously had abnormal results.
Women must be registered with a GP to be invited for a test.
In the US, tests start when women turn 21 and are carried out every three years until they reach 65.
Changes in cervical cells are often caused by the human papilloma virus (HPV), which can be transmitted during sex.
In January 2018, women shared selfies with smeared lipstick on social media to raise awareness of the importance of getting tested for cervical cancer in a campaign started by Jo’s Cervical Cancer Trust.
Celebrities including model and socialite Tamara Ecclestone, former I’m A Celebrity! star Rebekah Vardy and ex-Emmerdale actress Gaynor Faye joined in to support the #SmearForSmear campaign.
Socialite Tamara Ecclestone supported the Jo’s Trust’s #SmearForSmear campaign