THE stork has been busy in the entertainment scene. Singer Christina Aguilera, socialite Nicole Richie and actress Jessica Alba are celebrity mums who have chosen to have their first child before they hit 30.

Both Richie, at 26, and Aguilera, 27, gave birth to their first born in January this year. Alba, 24, is expecting to pop in three months' time.

"Start young if you're going to have children," espouses Dr Tan Thiam Chye, obstetrician and gynaecologist at Kadang Kerbau Women And Children's Hospital.

Dr Tan has also co-authored a book, The New Art And Science Of Pregnancy And Childbirth.

He explains that a woman's fertility is at its prime when she is between 20 and 24 years old, with a sharp decline from 35 years old onwards.

On average, there is a drop of 3 per cent in fertility with each increasing year.

Lifestyle choices, financial considerations, and career as a priority have all led to women having their first children past age 35, and some even in their 40s.

But a woman's body in her 20s is prepared to handle the demands of conceiving and carrying a child.

Dr Ann Tan, consultant obstetrician & gynaecologist at the Women & Fetal Centre at Mount Elizabeth Medical Centre and the current president of the Association Of Women Doctors Singapore, says that she sees about 30 to 40 per cent of patients having their first child between the ages of 24 to 30.

"Many women put off having children till later due to various concerns, whether it be that they are not settled in their career, or they haven't found the right partner, or that they don't want the responsibility of children yet," she says.

"But women in their 20s are at their most fertile, which means that conceiving is easier than in their later years."

Generally, women in their 20s may ovulate more often, have healthier eggs, and are at less risk for gynaecological problems ranging from fibroids and ovarian cysts to endometriosis (a condition where the tissue of the uterus grows outside of the uterus).

They are also less susceptible to high blood pressure, diabetes and thyroid problems.

The risk of having a Caesarean section is also higher for older women, and the risks of miscarriage increase if a woman is above age 35.

Women over 35 are also much less fertile.

And there are other reasons for a woman to have a child in her 20s.

Evelyn Tan, 33, who works in marketing at a cosmetics company, had her child, Trisha, when she was 29. She is glad she and her husband, producer Clarence Tan, 36, started their family relatively early.

Says Ms Tan: "I'm sure my energy level for my child will decrease as I age. I'm already worried that when she's a teenager and I'm in my 50s, I won't be quite as energetic as I am now."

"I thought, the longer I wait, the harder it may be to conceive," she says of having a baby under age 30. "We've been trying for another baby for the past year, and it's not as effortless as when we had Trisha."

Women in their 20s who are concerned about maintaining their figure have one more good thing going for them if they decide to have a child.

Doctors say that their bodies are generally quicker to recover from the trauma of childbirth than older women's.

"I've seen some women in their 20s bounce right back," says Dr Tan.

"A few are even back in their mini skirts two weeks after giving birth."