Obstructive sleep apnea (OSA) is prevalent in obese, pregnant Asian women with gestational diabetes, even when their diabetes is controlled by diet, a new study from Thailand finds. Study results, which also connect the severity of sleep disordered breathing with higher blood glucose levels and greater daytime sleepiness, were presented on Saturday at the Endocrine Society’s 97th annual meeting in San Diego.

In 25 women with diet-controlled gestational (pregnancy) diabetes, the researchers found a 56% prevalence of OSA, a sleep disorder in which a person stops breathing for brief episodes during sleep. This OSA prevalence is similar to how often nonpregnant adults with type 2 diabetes have OSA, according to the study authors.

“OSA may be an important co-morbidity [co-existing illness] in women with gestational diabetes mellitus,” says a study investigator, Sirimon Reutrakul, MD, associate professor at Mahidol University Faculty of Medicine, Bangkok, Thailand, in a release. “Our results will have to be confirmed in a larger study but potentially have an impact for patient care.”

As many as 9.2% of pregnant women develop gestational diabetes, the US Centers for Disease Control and Prevention estimates. Being overweight or obese is a risk factor.

Participants in the new study were considered obese using the World Health Organization cutoff for Asian women with a body mass index (BMI) before pregnancy of 25 kg/m2 or more. The women were between 24 and 34 weeks pregnant, and all had diet-controlled gestational diabetes.

OSA was diagnosed using a home monitoring device (Itamar Medical Watch-PAT200) worn on the participant’s wrist overnight. The US Food and Drug Administration has approved this device for detecting OSA. It measures overnight oxygen saturation, together with changes in peripheral arterial tone in response to breathing disruptions. Reutrakul says the Watch-PAT200 had a good correlation with polysomnography when tested in pregnant women and others.

Of the 14 study participants found to have OSA, 12 women had mild OSA and two had moderately severe OSA, the investigators reported. There were no differences between women who had OSA and those who did not have this sleep disorder other than a tendency for the OSA group to have a higher average prepregnancy BMI than the other group (31.2 vs 29.0 kg/m2).

In this study, lower oxygen saturation was strongly associated with greater reported daytime sleepiness. Also, the researchers found that the lower the lowest oxygen saturation level measured, the higher the level of blood sugar on the fasting blood glucose test. Although this study cannot determine causality—whether OSA leads to high blood sugar or vice versa—Reutrakul says previous studies in healthy humans show that lowering one’s oxygen level can lead to impaired glucose metabolism.

“If a future study confirms our results, the next step is to explore if treating OSA in these pregnant women will lead to better glucose control and pregnancy outcomes,” Reutrakul says.

Poor glucose control during pregnancy can lead to problems for both mother and child, including a higher chance of premature birth or stillbirth, according to the Hormone Health Network.