Mrs T, 45, a mother of three, anxiously related the following to me during her recent visit to my clinic.

"Two months ago, after my husband and I had sex, I noticed light pink stains on my underwear.

"I did not pay much attention as the spotting stopped the next day. The spotting recurred a few times, usually after sex. I did not think it was serious as the stains were very light. I thought it was due to stress on my part.

"When the spotting continued last month and became heavier, I began to worry and came to see you straight away."

She sees me every year to have her Pap smear done. This is a simple screening procedure in which cells from the neck of the womb (cervix) are scraped by a wooden spatula or small brush and smeared on a microscope slide.

The cells are examined for pre-cancerous or cancerous changes in the cervix. The test is not intended to detect other female cancers such as those of the ovary, vagina or uterus.

When I examined Mrs T, the cervix looked inflamed and red. It bled slightly on contact with the brush and there was a yellowish vaginal discharge. The Pap smear result indicated the presence of cancerous-looking cells.

I decided, on a further investigation using a type of microscope called a colposcope, to inspect the entire area of the cervix under magnification. To do this, the cervix was stained with a harmless dye to detect any abnormal tissue.

A directed biopsy was taken and a pathological examination revealed pre-cancerous abnormal tissues or lesions.

As Mrs T had decided not to have any more children, she and her husband opted to have her womb, including the cervix, removed (total hysterectomy). This was successfully done by key-hole surgery.

Pre-cancerous changes of the cervix are a state of abnormal cell growth which may progress to cervical cancer and usually develop in women between the ages of 25 and 40. Only some of the women with these changes will develop cancer after several years.

Every year, about 200 women in Singapore are detected with cervical cancer and about 100 die from the disease. It is the sixth most common cancer affecting women here - after cancers of the breast, large intestine, lung, ovary and uterus.

A number of factors may increase the risk of cervical cancer. These include previous infection with the human papilloma virus (HPV), early sexual contact, multiple sex partners, a weakened immune system (the body's natural defence system), cigarette smoking and taking birth control pills.

Almost all cervical cancers are related to HPV, a group of viruses that is transmitted usually through sexual contact. HPV infections are very common and condoms do not offer full protection.

About 50 to 80 per cent of women will acquire a genital HPV infection in their lifetime. There are over 100 types of HPV but only 15 types are known to cause cancer. HPV types 16 and 18 cause more than 70 per cent of all cervical cancers and are known as "high-risk" types. "Low-risk" HPV virus types do not cause cancer but can lead to genital warts.

HPV infections do not cause any symptoms and most will clear up by themselves. In a small number of women, the virus survives for years. It can then convert some cells on the surface of the cervix into pre-cancer cells. These changes happen very slowly and eventually lead to invasive cancer.

Women with many sex partners or whose husbands are promiscuous have a higher risk of developing cervical cancer. This is related to higher-than-average exposure to HPV infections.

Among women who are infected with the HPV virus, HIV infection (the virus that causes Aids) or taking drugs that suppress the immune system also increase the risk of cervical cancer.

Smoking cigarettes increases the risk of cervical cancer. Mrs T had been smoking for the past 20 years.

Taking birth control pills for five or more years may also increase the risk of cervical cancer.

Symptoms do not usually show up in pre-cancerous stages and early cervical cancer. Some women experience bleeding in between their periods or during and after sex, as in Mrs T's case.

Recently, two vaccines - Cervarix and Gardasil - have been developed to prevent pre-cancerous lesions. They are found to be highly effective when given at adolescence.

Besides preventive vaccination, early detection and prompt treatment remain the cornerstone in managing cervical cancer.

A key feature of cervical cancer is its slow progress. This presents a window of opportunity for prevention. If pre-cancerous lesions can be detected and treated promptly, cervical cancer can be prevented.

Dr Peter Chew is a senior consultant gynaecologist and obstetrician at Gleneagles Medical Centre. He is the founder chairman of aLife (www.alife.org.sg), a charitable organisation with a mission to nurture and promote healthy family life.

This story was first published in Mind Your Body, The Straits Times, on Dec 25, 2008.