Most of us are familiar with the term Irish twins - when siblings are born less than 12 months apart, sometimes even within the same calendar year. Until now, having babies close together was thought to increase the risk of prematurity and low birth weight, however a new study suggests that this may not be the case.

According to Australian researchers, previous studies have indicated that pregnancies that start less than two years after a previous birth may be more likely to lead to a premature birth and/or low birth weight.

It had been suggested that adequate spacing between births was necessary to allow a woman to recover from the physical effects of pregnancy.

The researchers decided to investigate this further. They analysed data relating to over 40,000 women who had given birth between 1980 and 2010. They found that the risk of a premature birth or low birth weight did not increase if there was a short interval between pregnancies.

They suggested that where a premature birth or low birth weight occurs, this is probably due to other factors which may be more common among women with pregnancies that occur close together.

"There may be more effective ways of reducing the risk of poor birth outcomes than by avoiding a short interval between pregnancies - for example, by eating well, maintaining a healthy weight, avoiding smoking and alcohol consumption, and seeking adequate medical care," they commented.

The researchers from the Telethon Kids Institute in Perth said that based on their findings, ‘mothers who fall pregnant again within two years should be reassured about the effects of the short interval'.

However, they acknowledged that the World Health Organization recommends that mothers should wait ‘two years between the birth of one child and starting to try for the next'.

"Our results are based on population averages, and there may be some situations where it is important to allow a sufficient time to recover between pregnancies," they added.

Details of these findings are published in the British Medical Journal.

For more information on pregnancy, see our Pregnancy Clinic here