Last updated at 1:32 AM on 29th July 2009
Many women with borderline results are given invasive treatment which increases their chances of suffering complications in future pregnancies
Hundreds of women may undergo unnecessary surgery after cervical smear tests, it has emerged.
Many women with borderline results are given invasive treatment which increases their chances of suffering complications in future pregnancies.
A study in the British Medical Journal found many of these treatments are entirely pointless, as there may be no tumour, or it may so small that it would disappear naturally.
Some 2,700 women are diagnosed with cervical cancer every year, and around 1,000 die.
The NHS screens women aged 25 and above for signs of pre-cancerous cells that may develop into tumours. It claims screening saves around 4,500 lives a year.
Many women with positive results are referred for a procedure known as a 'colposcopy' to carry out a more detailed investigation.
In many cases lesions are found, and the patients are sent for an operation to remove abnormal tissue - even though it may not be cancerous.
Some doctors argue the operation should only happen if a biopsy proves it is cancerous. The BMJ research found that for those whose tests reveal only mild changes or borderline results, invasive treatment can do more harm than good.
The study concluded that while the colposcopy detected more serious lesions (known as cervical intraepithelial neoplasia or CIN) it could lead to overtreatment, because they could sometimes return to normal of their own accord.
The study of more than 4,000 British women aged 20-59 whose results showed borderline or mild abnormalities also revealed a higher rate of after-effects.
These included pain, bleeding and complications in later pregnancies.
The study's authors stated: 'We conclude that there is no clear benefit of a policy of immediate colposcopy as although it detects more CIN grade II or more severe disease, it leads to a large number of referrals with no high-grade CIN, overtreatment with associated after effects in young women, and no clear psychological benefit.'