Media playback is unsupported on your device Media caption What happens during a smear test?

Early cell changes that can turn into cervical cancer may not need treatment and may get better on their own in 50% of cases, according to a new study.

The British Medical Journal research looked at the outcomes of more than 3,000 women and found half of the "moderate" lesions found on routine smear tests regressed spontaneously.

The study authors stress it is still very important that women attend for cervical screening when invited.

Regular screening saves lives.

What does a positive smear test mean?

Most women's smear test results will be normal, but for around one in 20, the test shows some abnormal changes in the cells of the cervix.

Although most of these changes will not lead to cancer and the cells may return to normal, some lesions will need to be removed to prevent them turning cancerous.

Currently, doctors may treat "moderate" pre-cancerous lesions, classified as CIN2, but leave and monitor low grade CIN1 lesions.

The CIN grading reflects how deep the cell changes go into the surface of the cervix - the neck of the womb:

CIN 1 - one-third of the thickness of the surface layer is affected

CIN 2 - two-thirds of the thickness of the surface layer is affected

CIN 3 - the full thickness of the surface layer is affected

What did the study find?

The BMJ research, which looked at CIN2 lesions, suggests:

More than half of all untreated cases will get better spontaneously within two years

Just under one-third will persist

Just under one in five will get worse

For women under 30 only, the rates were 60%, 23% and 11%.

That would mean that in 1,000 women aged under 30 with a diagnosis of CIN2: 600 will have regression, 230 will persist and 110 will have a lesion that will get worse and could become cancer, although the researchers stress that the findings are not a perfect prediction and should be interpreted with caution.

What should women do?

Prof Maggie Cruickshank, an expert from the University of Aberdeen, advises in a linked editorial in the BMJ: "Knowing that the chance of regression is 50%-60%, still means taking a gamble that surveillance is simply delaying treatment and even a small risk of cancer (0.5% in this study) may still be unacceptable to some."

But she notes: "The effects of local excision, such as pain, bleeding, or menstrual disturbance, time off work, and the possibility of pregnancy complications, including preterm birth and mid-trimester miscarriage are also important considerations in decision-making."

Robert Music from Jo's Cervical Cancer Trust: "The findings of this study should be treated with caution, as indicated by the researchers. However, some women can experience psychological or physical side-effects following treatment for abnormal cells so if further evidence indicates monitoring over treatment is sufficient in some cases then this is positive.

"If you are currently waiting for or going through treatment, please do not let this deter you. Further and more rigorous research is needed to fully understand the implications of this study."

All women who are registered with a GP are invited for cervical screening: