New research shows sleep disorders in women, such as sleep apnea and insomnia, increase the risk of giving birth before reaching full term, findings that could give doctors early warning of premature births.

It could also give medical teams a chance to minimise the risk of preterm births if these sleep disorders can be effectively managed during pregnancy.

According to the team from the University of California San Francisco, the research sheds some light on sleep disorders that often go undiagnosed in the midst of normal sleep changes that typically happen during pregnancy.

The study is the first to examine the effects of insomnia on pregnancy, and to make sure other factors contributing to preterm birth were separated out, the researchers used a case-control design: women were put in pairs based on matching risk factors, including smoking and hypertension, with the sleep disorder diagnosis the key difference.

"This gave us more confidence that our finding of an earlier delivery among women with disordered sleep was truly attributable to the sleep disorder, and not to other differences between women with and without these disorders," says lead researcher Jennifer Felder.

The results, based on 2,265 women with sleep disorders and the same number of matching controls, are pretty clear: the chance of preterm birth (before 37 weeks' gestation) was 14.6 percent for women diagnosed with a sleep disorder during pregnancy, compared to 10.9 percent for those who were not.

Meanwhile the odds of early preterm birth (before 34 weeks) was more than double for women with sleep apnea and nearly double for women with insomnia.

With the preterm rate about 10 percent in the United States, and more health complications associated with a preterm birth, this is a potential way to getting that percentage lower and saving lives along the way.

"What's so exciting about this study is that a sleep disorder is a potentially modifiable risk factor," says Felder.

Cognitive therapy is one potential treatment Felder's team is looking at to try and reduce that risk, as it's been shown to be effective in the general population and doesn't require any medication – an important consideration if you're pregnant.

In the larger dataset of nearly 3 million records from which the samples were pulled, very few women, well below 1 percent, were diagnosed with sleep disorders.

Compare that to the general population in the US, where sleep apnea is estimated to affect around 6.62 percent of people. For chronic insomnia, the figure is 10 percent.

The researchers think that shows a problem with identifying these issues in pregnancy, and are calling for improved and more widespread screening for these sleep problems.

Thanks to the large sample size, and the case-control methods used here, it's clear there's some connection between sleep disorders and premature birth – so let's hope the findings can be used to make a real difference in the number of pregnancies reaching full term.

The research has been published in Obstetrics & Gynecology.