23 Jul 2011
By Theresa Tan
THE ticking biological clock is never far from the minds of both doctors and women.
Doctors have long warned women against delaying motherhood, as the chances of getting pregnant fall while the risk of the pregnancies running into problems increases with age.
Take a 35-year-old woman, for example. Her chances of conceiving a baby when she has sex during her ovulation period are estimated to be half that of a 25-year-old, said Dr Peter Chew, a gynaecologist who runs the Peter Chew Clinic for Women. This is because women are born with a finite supply of eggs, which deteriorate in quantity and quality over time.
A woman is at her fertility peak between 20 and 25. After 35, her fertility "starts to decline more markedly". After 40, it falls "precipitously", he added.
The chances of miscarriage also rise with age. A woman under 35 has a 15 per cent chance of miscarrying; for those over 42, it rises to about 50 per cent.
Older would-be mums are also at higher risk of developing complications such as gestational diabetes, high blood pressure and other problems. They are also more likely to have a difficult labour.
Their babies are also at higher risk of carrying chromosomal abnormalities, such as Down syndrome, and structural abnormalities like heart or brain defects.
Growth problems, such as a baby not growing well, and unexplained stillbirths are also more common with older mums, said Dr Tan Lay Kok, a senior consultant at the Singapore General Hospital's obstetrics and gynaecology (O&G) department.
A recent study of almost five million children in the United States done by the University of California, Davis found that older mums are more likely to have an autistic child. Every five-year increase in a mother's age raised her risk of having an autistic child by 18 per cent.
The father's age, on the other hand, is a risk factor only when he has a child with a much younger woman. When the father is over 40 and the mother under 30, the increased risk is especially pronounced. Researchers say the reasons that older parents have a higher risk of having an autistic child are unknown.
However, the chairman of the KK Women's and Children's Hospital (KKH) O&G division said this is no cause for unnecessary alarm.
Associate Professor Tan Kok Hian said the study found the incidence rate of an older woman bearing an autistic child is "still very low". He added that more studies are needed to confirm the relationship between parents' ages and developmental problems in children.
theresat@sph.com.sg
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