Sleep disordered breathing (SDB) insidiously worsens metabolic function, heightens insulin resistance (IR), and in pregnancy is thought to precipitate gestational diabetes, preterm birth, growth restriction, gestational hypertension, and preeclampsia. Despite the fact that sleep disturbances are common during pregnancy, SDB remains under-recognized, under-diagnosed, and poorly understood, particularly in pregnancies affected by obesity. Sixty percent of pregnancies are now affected by obesity, yet the relationship between SDB, patterns of glycemia, and insulin resistance (IR) in obese pregnant women is a neglected area with major therapeutic implications to improve maternal and infant health. Using a prospective design in which diet and gestational age are highly controlled, the investigators propose to measure SDB (apneas/hypopneas) in obese pregnant women using an ambulatory sleep monitoring system. In parallel, robust patterns of glycemia will be measured with a continuous glucose monitoring system (CGMS), followed by a 75g oral glucose tolerance test to measure insulin action. The investigators global hypothesis is that worse SDB in part accounts for higher 24-hour patterns of glycemia in obese normal glucose tolerant (NGT) pregnant women in their 3rd trimester. We will test the hypothesis that: 1) In obese NGT pregnant women at 32-34 weeks gestation on a controlled eucaloric diet, higher apnea hypopnea index (AHI) will be positively associated with 24-hour glycemia measured by a CGMS and that, 2) Higher AHI in obese NGT pregnant women at 32-34 weeks gestation on a eucaloric controlled diet will be associated with higher insulin resistance measured by a 75g oral glucose tolerance test (Matsuda Model). Early identification and treatment has the potential to decrease long-term maternal cardiovascular morbidity and mortality.