Fewer IVF mums having twins, says study

The chances of having twins or other multiples after fertility treatment is falling, a new study shows.

The proportion of women using assisted reproductive technology (ART) who have twins is high because of the number of embryos transferred at each treatment cycle.

A report by the Australian Institute of Health and Welfare (AIHW) released on Thursday showed the proportion of multiple pregnancies resulting from ART fell from 19.4 per cent in 1994 to 18.1 per cent in 2003.

At the same time the number of treatment cycles between 2002 and 2003 increased by nine per cent.

AIHW spokesman Professor Michael Chapman said the change reflected a fall in the number of embryos being transferred per cycle in Australia and New Zealand.

Prof Chapman said 10 years ago, three or more embryos were transferred in almost half of all embryo transfer cycles.

The figure had fallen to 4.3 per cent of transfer cycles in 2003, he said.

The study showed 39,720 treatment cycles were attempted in Australia and New Zealand, resulting in 8,365 pregnancies.

Just over one-in-five resulted in miscarriage or ectopic pregnancy, while 1,141 were twin births and 22 resulted in triplets.

The report also found women who entered fertility programs earlier in life had a better chance of a successful birth.

"When we look at the ages of women who used their own fresh embryos, women aged 25 to 29 years achieved more successful outcomes, with 35.1 per cent of embryo transfer cycles achieving a live delivery," Prof Chapman said.

"Women aged 40 to 44 years had a success rate of 9.5 per cent."

Women on fertility programs are also improving their chances of having average birthweight babies and delivering them full-term.

Low birthweight's and pre-term deliveries are a common problem with ART treatment.

The study showed just over one in four ART babies were being born pre-term - an improvement on one-in-three babies in 2000.

Babies born with low birthweight (less than 2.5kg) made up 21.8 per cent of babies born in 2003, down from 26.4 per cent in 2000.