AIHW media releases

Multiple births, especially twin births, have been rising over the last decade, according to a report released today by the Australian Institute of Health and Welfare (AIHW).

Australia's Mothers and Babies 2001 features special chapters on twin births and assisted reproductive technology (ART). The report shows that 4,062 mothers gave birth to twins out of 4,157 mothers with multiple pregnancies recorded in Australia in 2001. In comparison there were 3,455 recorded multiple confinements in 1992.

Around 1.7% of mothers giving birth in 2001 had multiple pregnancies, with a twinning rate of 16.2 per 1,000 confinements.

Head of the AIHW's National Perinatal Statistics Unit, Dr Elizabeth Sullivan, says the rise in twin births can be attributed to a number of factors, including delay in childbearing, older mothers, use of fertility drugs and assisted reproductive technology.

'The average age of all mothers in 2001 was 29.2 years, but mothers of twins were older, with 25% aged 35 or over, compared with 17% for mothers of singleton babies.

'Also, of the 3,916 mothers giving birth in 2001 following ART treatment, 21% were to sets of twins.'

More generally, says Dr Sullivan, the report shows the steady trends of the last 10 years continuing with the proportion of women having caesarean sections increasing to 25% compared to the 18% recorded for 1992.

'Although reasons for women having caesarean sections are not collected, some descriptive characteristics of the women are available. Women giving birth to twins were more likely to undergo a caesarean section, as were women who were non-Indigenous, or who had received their care in a private hospital or were aged 35 years and older.

'Just under one in two women giving birth following ART also had had a caesarean section.'

Other factors in the increase in caesarean section rates are the decline in vaginal breech and instrumental deliveries. During the period 1992-2001, instrumental deliveries (forceps, vacuum extraction) have decreased slightly, from 12% to 11%.

Other findings from the report include:

• Teenage mothers accounted for 5% of all mothers in 2001 (a decline of 14% over the decade from 1992 to 2001).
• 3.6% of all mothers were Indigenous Australians, with an average age of 24.5 years and with a high proportion (23%) being teenage mothers in 2001.
• 41% of all mothers were having their first baby, and 34% were having their second in 2001.
• Average age of mothers having their first baby in 2001 was 27.5 years.
• 7.8% of all births were recorded as preterm (less than 37 weeks gestation).
• Mothers continued to have relatively short postnatal stays in hospitals in 2001, with 10.8% of mothers staying for less than 2 days, and 56.4% staying between 2 and 4 days.