Pregnant women with a sleep disorder which causes them to snore loudly could be more likely to have smaller babies, researchers have found.
A small study of 41 pregnant women in Victoria found a trend among women with obstructive sleep apnoea to have babies whose growth rates slowed before birth or who had low weights at birth compared to babies of women without the disorder.
People with obstructive sleep apnoea tend to snore heavily and have frequent brief episodes where they stop breathing altogether, or have reduced airflow because their airway collapses.
Lead researcher Dr Alison Fung, a consultant obstetrician at Melbourne's Mercy Hospital for Women, said the findings should not alarm pregnant women who snore, as more research was needed.
"We have found a trend toward slowed growth with obstructive sleep apnoea, but need to confirm it," she said.
"Not all snorers will have sleep apnoea but in general those with sleep apnoea will snore and choke and have disrupted sleep."
Of the 41 women who took part in the study, 10 had obstructive sleep apnoea.
Half the babies born to those women either had low birth weights or had experienced a 30 per cent drop in their growth rates during the weeks leading up to their birth.
The same results applied to just six out of the 31 babies born to women without the sleep disorder.
While not all pregnant women will have sleep apnoea, between 20 and 35 per cent are estimated to snore during pregnancy.
Those who do develop sleep apnoea usually find the disorder disappears after they have their baby.
Pregnant women tend to snore because of the increased levels of the hormone progesterone, which causes increased stuffiness in the airways and congestion in the nasal passage.
Their diaphragm also rises as the baby grows inside the uterus, reducing their lung capacity.
Increased swelling in late pregnancy and weight gain, the biggest link to sleep apnoea in the general population, also play a role.
Dr Fung said pregnant women could try to prevent snoring by lying on their side to help them breathe faster and protect against airway collapse.
They could also consider a continuous positive airway pressure mask to keep their airways open.
Dr Fung, who is presenting her research at the forthcoming Australasian Sleep Conference in Sydney, hopes to begin a larger study on sleep apnoea in pregnant women in 2012.
"Further research is still required to confirm these findings in the first instance, and if the results are verified, we plan to investigate this further in high-risk populations and to also investigate options for treatment," she said.