Severe maternal sleep-disordered breathing (SDB) is a known risk factor for gestational diabetes, which is commonly diagnosed in the second or third trimester of pregnancy.

Now, a new study suggests that increases in insulin resistance, a precursor for gestational diabetes, may take place as early as the first trimester of pregnancy in women with risk factors for obstructive sleep apnea (OSA), such as overweight and habitual snoring.

This finding could potentially provide physicians with a window of opportunity to improve outcomes by screening at-risk women early in pregnancy or even prior to conception, Laura Sanapo, MD, assistant professor of medicine (research) at Brown University, Providence, R.I., and colleagues wrote in Sleep.

“Further studies are needed to investigate the association and its impact on the development of gestational diabetes, and to establish whether early-gestation or pregestational treatment of SDB would improve glucose metabolic outcomes in pregnancy,” they wrote.

“What this paper demonstrates is that the changes that predate gestational diabetes are seen much earlier in pregnancy,” senior study author Ghada Bourjeily, MD, professor of medicine at Brown University, said in an interview. Women should be screened for SDB rather than insulin resistance in early pregnancy since continuous positive airway pressure therapy (CPAP) is a highly effective intervention.

Waiting until midpregnancy to screen for OSA “is too late to make significant changes in the care of these women,” said Bourjeily, who is also director of research and training at the Women’s Medicine Collaborative at The Miriam Hospital in Providence, R.I. “By the time you diagnose gestational diabetes, the cat is out of the bag.”

For the study, women with early singleton pregnancies and risk factors for OSA such as habitual snoring and a median body mass index (BMI) of at least 27 kg/m2 were recruited from two prospective clinical trial studies enriched for OSA positivity. Women with a history of pregestational diabetes and those using CPAP or receiving chronic steroid therapy were excluded from the current study.

A total of 192 study participants underwent in-home sleep study (HSAT) and homeostatic model assessment (HOMA) between 11 and 15 gestational weeks, respectively. The association between continuous measures of SDB as a respiratory-event index as well as oxygen-desaturation index and glucose metabolism parameters such as insulin resistance (HOMA-IR) were analyzed after adjusting for gestational age, maternal age, BMI, ethnicity, race, and parity.

In all, 61 women (32%) were diagnosed with OSA based on respiratory event index values greater than or equal to five events per hour. These participants were more likely to be older, to have a high BMI, and to be multipara, compared with women who didn’t have a diagnosis of OSA. Women with a diagnosis of OSA exhibited higher glucose and C-peptide values and a higher degree of insulin resistance, compared with women without OSA, the researchers found. An increase of 0.3 in HOMA-IR related to maternal SDB in early pregnancy may significantly affect glucose metabolism.

Although the findings of the current study cannot be extrapolated to women who don’t have overweight or obesity, some women with normal-range BMI (18.5-24.9) are also at increased risk of glucose metabolism changes, Bourjeily pointed out. This includes those of Southeast Asian descent. “We found that the association of SDB parameters with insulin resistance was actually happening independently of BMI and other factors.”

Ideally, screening for SDB would begin prior to pregnancy, Bourjeily said. A BMI greater than 25 should be taken into account and patients asked if they snore and if so, whether it’s loud enough to wake their partner. They should also be asked about experiencing daytime sleepiness.

“Based on these answers, especially in women screened prior to pregnancy, there will be time to make the diagnosis of sleep apnea and get the patient on CPAP,” Bourjeily said.

“This is an interesting study and one of the rare ones looking at early pregnancy and some of the mechanisms that could possibly be contributing to gestational diabetes,” commented Grenye O’Malley, MD, assistant professor in the division of endocrinology, diabetes, and bone disease at the Icahn School of Medicine at Mount Sinai, New York. O’Malley was not involved in the study.

“It confirms our suspicions that there’s probably a lot of things happening earlier in pregnancy before a diagnosis of gestational diabetes. It also confirms that some of the mechanisms are probably very similar to those involved in the association between disordered sleep and the development of type 2 diabetes.”

However, it’s too early to determine whether screening for SDB and the use of CPAP will prevent glycemic changes, O’Malley said in an interview. “Whenever we screen, we ask whether we have an intervention that changes outcomes and we don’t know that yet.”

Some of the symptoms of SDB are also common in early pregnancy, such as a BMI greater than 25 and daytime sleepiness, O’Malley pointed out. It was unclear whether the study participants had a propensity to develop type 2 diabetes or whether they were at risk of gestational diabetes.

This study was funded by the National Heart, Lung, and Blood Institute; the National Institute for Child Health; and the National Institute of General Medical Sciences. Bourjeily and colleagues, as well as O’Malley, reported having no potential financial conflicts of interest.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.

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