Study Objective: To assess the validity of using the Apnea Risk Evaluation System (ARES) Unicorder for detecting obstructive sleep apnea (OSA) in pregnant women. Methods: Sixteen pregnant women, mean age (SD) = 29.8 (5.4) years, average gestational age (SD) = 28.6 (6.3) weeks, mean body mass index (SD) = 44.7 (6.9) kg/m 2 with signs and symptoms of OSA wore the ARES Unicorder during one night of laboratory polysomnography (PSG). PSG was scored according to AASM 2007 criteria, and PSG AHI and RDI were compared to the ARES 1%, 3%, and 4% AHIs calculated with the ARES propriety software. Results: Median PSG AHI and PSG RDI were 3.1 and 10.3 events/h of sleep, respectively. Six women had a PSG AHI ≥ 5 events/h of sleep and 11 had a PSG RDI ≥ 5 events/h of sleep. PSG AHI and RDI were strongly correlated with the ARES AHI measures. When compared with polysomnographic diagnosis of OSA, the ARES 3% algorithm provided the best balance between sensitivity (1.0 for PSG AHI, 0.91 for PSG RDI) and specifi city (0.5 for PSG AHI, 0.8 for PSG RDI) for detecting sleep disordered breathing in our sample. Conclusions:The ARES Unicorder demonstrated reasonable consistency with PSG for diagnosing OSA in this small, heterogeneous sample of obese pregnant women. S C I E N T I F I C I N V E S T I G A T I O N SP regnancy results in physiological changes that increase the risk of sleep disordered breathing (SDB). For instance, mechanical changes in gravid women-such as rapid weight gain and increased intra-abdominal pressure-result in decreased functional residual capacity and reduced oxygen reserve 1 and increase the risk of upper airway collapsibility. Other risk factors for SDB in pregnancy include increases in nasal congestion, Mallampati score, and snoring, andparticularly in pregnant patients who develop preeclampsiadecreases in upper airway size. [2][3][4][5][6][7] SDB in pregnancy has a negative impact on fetal outcomes. 8,9 A retrospective analysis compared 57 pregnant women with sleep apnea to 57 obese controls and 57 normal weight controls and showed higher rates of low birth weight and prematurity in women with OSA compared to obese and normal weight controls.10 Another study linking nation-wide population-based datasets in Taiwan showed that women with OSA (n = 791) were at an increased risk for preterm birth and small for gestational age compared to women without a diagnosis of OSA (n = 3,955), even after adjusting for multiple confounders. 11SDB also results in adverse outcomes in pregnant women. 12,13 In our recent study of 1,000 postpartum women, symptoms of SDB during pregnancy (measured with the multivariable apnea ) were associated with a greater than two-fold increased risk of gestational hypertensive disorders, gestational diabetes, and unplanned Caesarean deliveries. Validation of the Apnea Risk Evaluation System (ARES) Device13 Furthermore, from a physiologic standpoint, the impact of apneic episodes in pregnancy seems to be more potent than in non-pregnant women. In response to apneas, pregnant patients show a m...