DENVER (FRONTLINE MEDICAL NEWS) – Pregnant women with sleep apnea are more likely to have planned obstetric interventions, results of an Australian population-based cohort study suggest.

The study included all 636,227 in-hospital births during 2002-2012 in New South Wales, Australia’s most populous state. Maternal sleep apnea was also associated with increased rates of planned preterm birth, even though preterm birth is widely considered the greatest contributor to neonatal morbidity and mortality, Yu Sun Bin, PhD , said at the annual meeting of the Associated Professional Sleep Societies.

“Somewhere along the line, clinicians decided that the risks of preterm birth to the baby were outweighed by the risks to the mother of delivering at term,” said Dr. Bin of the University of Sydney.

She and her coinvestigators undertook this study because even though previous studies have linked maternal sleep apnea to increased risks of gestational diabetes and gestational hypertension, most of the prior studies were small, cross-sectional, and/or relied upon snoring as a proxy for sleep apnea, which many sleep specialists consider invalid.

The investigators compared maternal and infant outcomes for mothers with a documented diagnosis of sleep apnea – either central or obstructive – in the year before or during pregnancy with outcomes for mothers without that diagnosis.

There were 519 mothers with diagnosed sleep apnea, for a prevalence of 0.08%. That figure is low in light of other evidence, making it likely that the 635,708 women in the no-sleep-apnea group actually included a substantial number of mothers with undiagnosed sleep apnea. Thus, the investigators’ estimates of the adverse impacts of sleep apnea in pregnancy are “rather conservative,” according to Dr. Bin.

Australian women with sleep apnea were older and less healthy than mothers without sleep apnea were. They had higher baseline rates of obesity, preexisting diabetes, chronic hypertension, and were more likely to be smokers.

The incidence of pregnancy hypertension was 19.7% in the sleep apnea group and 8.7% in controls. In a multivariate regression analysis adjusted for potential confounders, the maternal sleep apnea group had a 40% greater risk of developing hypertension than did controls. However, contrary to previous smaller studies, they did not have a significantly increased rate of gestational diabetes.

Even after controlling for both pregnancy hypertension and gestational diabetes, the sleep apnea group still had a significant 15% increase in the relative likelihood of a planned delivery.

The rate of preterm birth at 36 weeks or earlier was 14.5% in the maternal sleep apnea group, compared with 6.9% in controls, for an adjusted 1.5-fold increased relative risk.

Perinatal death occurred in 1.9% of the sleep apnea group and 0.9% of controls; however, the resultant adjusted 1.73-fold increased risk didn’t attain statistical significance because of the small number of deaths in the study. Dr. Bin said she and her colleagues plan to further investigate this signal to learn whether it is real or an artifact of small numbers.

The incidence of 5-minute Apgar scores below 7 was 4.6% in the sleep apnea group, compared with 2.4% in controls, for an adjusted 1.6-fold increased risk. The rate of neonatal intensive care unit admission in the sleep apnea group was 27.9%, versus 16% in controls, for a 1.61-fold increased relative risk.

The NICU admission rate for preterm infants didn’t differ between the two groups. The difference occurred in term babies, whose NICU admission rate was 20.3% if they were in the sleep apnea group, but just 12.1% in the control group.

“This suggests that maternal sleep apnea is contributing to some condition in the baby that requires additional support,” Dr. Bin observed.

The nature of that condition, however, remains unclear, since all patient data available to the investigators was deidentified.

The incidence of small-for-gestational-age babies was similar in the sleep apnea and control groups. In contrast, the large-for-gestational-age rate was 15.2% in the sleep apnea group, compared with 9.1% in controls, for an adjusted 1.27-fold increased risk.

The two main limitations of the Australian study were the likely underdiagnosis of sleep apnea and the lack of any information on treatment of affected patients, according to Dr. Bin. A key unresolved question, she added, is whether interventions for maternal sleep apnea reduce the risks identified in the New South Wales study. She noted that one 16-patient randomized study of nasal continuous positive airway pressure suggests the answer is yes ( Sleep Med. 2007 Dec;9:15-21 ).

The Australian National Health and Medical Research Council supported the study. Dr. Bin reported having no financial conflicts.


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