Why do perfectly healthy women develop certain pregnancy complications? For some, sleep apnea's to blame. According to a study by the University of Medicine and Dentistry of New Jersey in New Brunswick, sleep apnea quadruples the chances of high blood pressure in pregnancy and doubles the risk of gestational diabetes.

Though this breathing disorder affects less than 1 percent of women of childbearing age, it's much more common in those who are pregnant, since weight gain and hormonal changes can interfere with breathing. The condition causes your airway to narrow and breathing to stop momentarily-sometimes hundreds of times a night. The lack of oxygen puts your body into "fight or flight" mode, pumping out hormones like adrenaline and cortisol, which send blood pressure soaring. Your body also produces more glucose so there's plenty of energy to respond to the "threat." Over time, diabetes can develop.

Fortunately, women may be able to prevent or manage their pregnancy complications through sleep-apnea treatment, which usually involves inhaling air from a machine during the night. Sounds scary, but take heart: Pregnancy-related apnea usually resolves or improves after the baby is born.