The purpose of this study is to see whether the presence of night-time breathing disturbances ("sleep-disordered breathing") in pregnant women is related to fetal growth patterns. The hypothesis is that fetal growth slows in the 3rd trimester in women with sleep-disordered breathing. Use of a nighttime breathing therapy called auto-PAP could minimize the slowing in fetal growth.

Inclusion Criteria:

• at least 18 years old;
• no more than 20 weeks pregnant;
• pregnant with one baby;
• found to have sleep-disordered breathing as measured by a sleep study. If you are found to have severe sleep apnea on the sleep study you will be referred for clinical care instead of participating in the study.

Exclusion Criteria:

• more than 20 weeks pregnant;
• pregnant with twins, triplets, or more babies;
• a current smoker, drink alcohol, or use recreational drugs;
• currently using positive-airway pressure therapy for treatment of obstructive sleep apnea;
• diagnosed with certain conditions such as bullous lung disease, a bypassed upper airway, pneumothorax (collapsed lung), pneumocephalus (leak of cerebrospinal fluid, the fluid that the brain and spine float in), if you have had recent trauma, or recent nasal surgery.

through delivery up to a maximum of 33 weeks