Large numbers of women are putting off having babies, resulting in more pregnancies affected by Down syndrome and more terminations of those pregnancies.
A study in England and Wales has found the number of women aged in their 40s having children has nearly doubled in a decade.
In New Zealand,Peter Stone, professor of maternal foetal medicine at the University of Auckland, said the median age for women in this country having babies was also increasing. He said New Zealand did not have easy access to statistics comparable with the British figures, but "we are likely to have the same issues".
Diane Ormsby, a Victoria University lecturer who specialises in reproductive biology, said the median age of women giving birth in New Zealand had increased to 30, from 25 in 1969, and the frequency of babies born with Down syndrome increased with maternal age.
She said in the student newspaper Salient that with New Zealand women tending to give birth later in life, the country was likely to see more aborting of fetuses with Down syndrome. That did not take into account changes in antenatal testing.
The International Clearing House for Birth Defects reported that in 2006, 63 New Zealand babies were born alive and affected by Down syndrome. The numbers of affected stillbirths and terminations were not reported.
From 1987 to 1991 - the last period for which both births and abortions related to Down syndrome were reported - the incidence of both rose rapidly with age from 9.28 per 10,000 in women aged 30 to 34 years, to 34.3 for women aged 35-39 years, and 452 for women aged 40-44.
Since then the number of older women having babies in New Zealand has increased substantially.
