Association of Body Fluid Distribution With Obstructive Sleep Apnea in Pregnant Women With Body Mass Index ≥ 40 kg/m2

Inclusion Criteria: * Participants who give written informed consent * Pregnant women in the third trimester of pregnancy * Grade III obesity * Patients who have prior diagnosis of OSA within the last one year, and non-compliant to treatment such as continuous positive airway pressure (CPAP), or dental appliance * Patients suspected to have OSA based on screening questionnaire (see page 2, OSA-Diagnostic tools for further details) Exclusion Criteria: * Fluid overload states including renal disease, liver disease and congestive heart failure * Prior history of vascular surgery in the lower limbs such as varicose vein surgery, vascular by-pass surgery or evidence of venous efficiency. * Patients with metal implants in lower limbs or spine, due to possible interference with the leg impedance signals. 58 * Participants with diagnosed OSA treated with Continuous Positive Airway Pressure (CPAP). * Patients requiring urgent sleep physician referral (within four weeks) due to serious medical conditions or safety critical-occupations according to the 2011 Canadian Thoracic Society (CTS) guideline 59 e.g. unstable ischemic heart disease, recent cerebrovascular disease. * Implantable cardiac devices