Seventeen-year-old Jen (not her real name) slept with a 23-year-old man because her friends were already "doing the same thing".
At that time, she had low self-esteem, partly because her older sister was doing well in her studies and she felt neglected by her parents.
"The man showered her with love and concern, so she agreed to have sex with him," said Mr Rahman Katama, a counsellor at the Department of Sexually Transmitted Infections Control (DSC) Clinic who handled Jen's case late last year.
But Jen later learnt that the man had been having unprotected sex with several other women. By then, she had contracted chlamydia.
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The bacterial infection can be cured with antibiotics without risk to the foetus.
But if left untreated, chlamydia may lead to an infection in the womb and fallopian tubes that causes problems like abdominal pain, infertility and even an abnormal pregnancy.
Jen's mother accompanied her to DSC Clinic for treatment. There, the teen was also counselled on how to protect herself from similar infections.
She expressed her fears and regret about getting infected, and said she would abstain from sex until she gets married.
The mother-daughter pair also had a heart-to-heart talk, said Mr Rahman, and the older woman admitted she could have been more attentive to her younger daughter.
Mr Tan Ee Han, senior counsellor at DSC, noted that parents tend to be angry and frustrated when they find out their child has a sex infection. But they would become more supportive eventually.
Referring to Jen's case, Mr Rahman said: "Her mother was upset but she wanted to do better.
"I believe they now have a better relationship," he added.