The study shows that the severity of OSA is much higher in women during late pregnancy than it is after they have given birth.  This includes an increased number of pauses in breathing, reduced oxygen saturation levels, and approximately two times as many arousals from sleep.  While results also show that overall blood pressure levels during sleep are only moderately elevated in late pregnancy, these levels fluctuate severely due to the cycles of pauses in breathing.  

OSA is a common disease that affects an estimated 6.5 percent of women who are of childbearing age, according to background information in the article.  Snoring, which is linked to a greater risk of breathing disorders during sleep, is much more prevalent during pregnancy, occurring in an estimated 14 percent to 23 percent of pregnant women.  OSA is an established cause of high blood pressure, and it may have other adverse effects upon both maternal and fetal health.

Natalie Edwards, Ph.D., of the University of Sydney in Australia, and colleagues find in the results of their study important implications affecting the provision of sound prenatal care.

“Physicians currently have the tendency to believe that pregnancy is protective against the development of OSA and are therefore less likely to consider symptoms that are indicative of sleep-disordered breathing,” says Dr. Edwards, “and this increased level of OSA during pregnancy may remain undiagnosed.”

According to the authors, increases in the levels of progesterone and estrogen are physiologic factors associated with pregnancy that are likely to play a role in exacerbating sleep-disordered breathing.  They did not find an association between the weight gain related to pregnancy and the increased severity of OSA.

The longitudinal study involved 10 women who were referred to a sleep clinic during the third trimester of pregnancy with suspected OSA.  Each participant underwent two overnight sleep studies by portable polysomnography in her home.  One study occurred during the third trimester of pregnancy, and the second study was performed between three and six months after giving birth.

Once diagnosed with moderate or severe OSA, each of the subjects was given nasal CPAP therapy for the remainder of their pregnancy.  To ensure an accurate comparison of results from the two sleep studies, however, this therapy was withdrawn soon after giving birth, at least three months prior to the second sleep study.  

This study was supported by a project grant from the National Health and Medical Research Council (NHMRC) of Australia. 

The journal SLEEP is the official publication of the Associated Professional Sleep Societies, LLC, a joint venture of the American Academy of Sleep Medicine and the Sleep Research Society.  It is a peer-reviewed research and clinical journal addressing sleep, circadian rhythms, and the diagnosis and treatment of the broad spectrum of sleep disorders.