• Ville Rimpilä, Riina Jernman, Katariina Lassila, Jukka Uotila, Heini Huhtala, Johanna Mäenpää, and Olli Polo.
• Faculty of Medicine and Life Sciences, University of Tampere, PL 100, 33014, Tampere, Finland; Unesta Research Center, Näsilinnankatu 48 D, 4th Floor, 33520, Tampere, Finland. Electronic address: rimpila.ville.p@student.uta.fi.
• Sleep Med. 2017 Aug 1; 36: 67-74.

ObjectiveSleep during pregnancy involves a physiological challenge to provide sufficient gas exchange to the fetus. Enhanced ventilatory responses to hypercapnia and hypoxia may protect from deficient gas exchange, but sleep-disordered breathing (SDB) may predispose to adverse events. The aim of this study was to analyze sleep and breathing in healthy pregnant women compared to non-pregnant controls, with a focus on CO2 changes and upper-airway flow limitation.MethodsHealthy women in the third trimester and healthy non-pregnant women with normal body mass index (BMI) were recruited for polysomnography. Conventional analysis of sleep and breathing was performed. Transcutaneous carbon dioxide (TcCO2) was determined for each sleep stage. Flow-limitation was analyzed using the flattening index and TcCO2 values were recorded for every inspiration.ResultsEighteen pregnant women and 12 controls were studied. Pregnancy was associated with shorter sleep duration and more superficial sleep. Apnea-hypopnea index, arterial oxyhemoglobin desaturation, flow-limitation, snoring or periodic leg movements were similar in the two groups. Mean SaO2 and minimum SaO2 were lower and average heart rate was higher in the pregnant group. TcCO2 levels did not differ between groups but variance of TcCO2 was smaller in pregnant women during non-rapid eye movement (NREM). TcCO2 profiles showed transient TcCO2 peaks, which seem specific to pregnancy.ConclusionsHealthy pregnancy does not predispose to SDB. Enhanced ventilatory control manifests as narrowing threshold of TcCO2 between wakefulness and sleep. Pregnant women have a tendency for rapid CO2 increases during sleep which might have harmful consequences if not properly compensated.Copyright © 2017 Elsevier B.V. All rights reserved.

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