The 35-year-old housewife swims for 45 minutes every Sunday and goes for brisk walks for 20 minutes twice a week.
Now 5 1/2 months pregnant, she said: "When I was pregnant with my first child, Darren, my back was so bad one week before I was due to deliver, I couldn't walk or get out of bed.
"I have no back pain this time." Ms Lee also developed high blood pressure when she was pregnant with Darren in 2005.
She does not have this condition with her current pregnancy, something she attributes to her regular exercise routine.
In fact, Ms Lee feels so fit that she has signed up for the 5km run at the Great Eastern Women 10K 2009 on Nov 1.
She participated in the 5km run at this year's Shape Run in July. She said: "I was in my first trimester then and I had the flu but I still jogged and brisk-walked. I found completing the 5km very manageable."
She started running thrice a week for an hour each time a year ago. Ms Lee said: "I wanted to keep fit and I felt I was putting on weight. My husband and I also wanted to try for baby No.2 and I knew I had to get healthy for that."
When she learnt about her pregnancy earlier this year, she sought her gynaecologist's advice about exercising.
Her doctor told her it would be better to brisk walk or swim rather than run, so Ms Lee switched to these forms of exercises.
She has also been eating healthier meals, cutting down on her intake of refined carbohydrates like white bread, and cooking white rice together with its healthier alternative, red rice.
She said: "Whenever I put on weight, whether I'm pregnant or not, my back tends to start hurting. Exercise makes a big difference."
This article was first published in Mind Your Body, The Straits Times.