Miss Goh Chern was perplexed and deeply unsettled.

She was spring cleaning her parents' flat for Chinese New Year when she found a birth certificate for a baby girl named Diana Tan, born on the same day as she was, 20 years ago.

She did not recognise the mother's name and there was no name listed for the father.

Who was Diana Tan?

Inside, she felt dread rising.

There had been other telltale signs earlier.

Her blood group was B+, totally unrelated to her parents' blood types of O+ and A+.

Unable to bottle up her fears any longer, she finally confronted her parents.

Am I adopted, she asked.

They flatly denied it but she could tell they were keeping something from her.

Heartbroken, she struggled to come to terms with the revelation.

"Everyone in the extended family knew I was adopted, except me," she said. "My sense of the truth was shattered, not knowing who I was and where I had come from. Every day, while taking the bus, I would look around to see who looked like me, hoping to find my birth parents."

It was only after a year that her mum finally told her the truth. She learnt that she had been given up for adoption as she had been born out of wedlock.

The news was hard to bear, particularly as she had only recently recovered from a protracted illness of the heart.

But as with that ordeal, she survived this one as well.

Now a 28-year-old teacher who reclaimed her birth name of Diana, Miss Goh has made peace with her parentage and wants to share the love she received from her adoptive parents with her students.

The biology teacher said: "I feel I owe my life to my parents. That was one of the biggest reasons I entered teaching: I want to love other children and impact lives as mine has been impacted."

Miss Goh's parents had been with her through thick and thin. When she was 12 years old, she awoke one day to find her heart beating wildly, leaving her breathless and dizzy. The doctor said her pulse was 240 beats per minute, well above the normal range of 60 to 100 beats.

She needed surgery to treat the problem, which was called Wolff-Parkinson-White Syndrome, a rare condition in which there is an extra circuit in the heart, leading to episodes of rapid heart rates. It can be fatal, resulting in heart failure or sudden cardiac death.

But she refused surgery, afraid of going under the knife. Besides, her parents were fruit sellers in a market and the only child did not want to burden them with the medical fees, which she recalled would have been around $10,000.

Over time, however, her condition worsened, becoming at times so bad she could not even sit up, let alone go to school, for weeks.

She said: "I could not do anything. I could feel my heart palpitating very fast when I tried to sit up, so I had to lie down."

In the end, at the age of 13, she had the first of three operations to fix the problem. But the palpitations continued.

Things came to a head in Secondary 3, when her father suffered a heart attack and had to stop working. Her mother took on odd jobs, such as cleaning toilets, to make ends meet.

In the meantime, Miss Goh's heart problem was not getting any better. Once, she was taking part in a debate competition at school when she collapsed from the palpitations. That year, she had her second heart operation.

It took a third operation when she was 19 years old to finally set things right. Miss Goh has not had any problems with her heart since then.

Despite her health woes, she excelled in her studies. She scored eight distinctions in the O-level examinations, four As at the A levels and graduated with first-class honours in life sciences from the National University of Singapore.

She did all this while holding down a part-time job after her A levels as a tutor to help pay the bills at home.

It was just as she felt life was getting better that the truth about her birth came like a bolt from the blue.

Miss Goh eventually tracked her biological mother down from the address on the birth certificate, but she declined to say more about their meeting. It also took about a year for her to come to terms with her adoption and smooth things over with her adoptive parents.

Her mother is now 74. Her father died in 2012 after another heart attack.

With the benefit of hindsight, she realised they had hid the truth from her so that she would not feel abandoned or unwanted, she said. Their decision, though hard to accept initially, stemmed from a place of love.

She said life has taught her that there are many sides to any situation, and one chooses what to focus on. As for herself, Miss Goh said she tries to see the positive in the most negative of circumstances.

Despite - or perhaps because of - the trials she has faced, Miss Goh's heart tends to go out to the less fortunate.

While still at school, she would volunteer once a week to tutor chronically ill children at Club Rainbow, a charity which helps children with life-threatening illnesses. She also volunteered regularly to teach adults with intellectual disabilities life skills, like personal hygiene, at the Movement for the Intellectually Disabled of Singapore.

"I have learnt that a person's most useful asset is not a head full of knowledge, but a heart full of love, an ear ready to listen and a hand always willing to help others," she said.

"If I were not adopted, I could have been in an orphanage. I feel so lucky to have a home and that my parents loved me dearly."