Sleep apnea is associated with a greatly increased incidence of pregnancy-induced diabetes and high blood pressure, according to a study.

The study found that when the women's weight was taken into account, sleep apnea was associated with a doubling of the incidence of gestational diabetes and a fourfold increase in the risk of pregnancy-induced hypertension.

In obstructive sleep apnea, the upper airway narrows, or collapses, during sleep. Periods of apnea end with a brief partial arousal that may disrupt sleep hundreds of times a night. Obesity is a major risk factor for sleep apnea.

The most effective treatment for sleep apnea is an apparatus called nasal CPAP, for continuous positive airway pressure, which delivers air through a mask while the patient sleeps, keeping the airway open.

The researchers analyzed data from all pregnancies associated with sleep apnea, gestational diabetes (women who developed diabetes during pregnancy) and pregnancy-induced high blood pressure nationwide in 2003. Out of almost 4 million deliveries, 452 had sleep apnea. Of the 167,227 women who had gestational diabetes, 67 had sleep apnea. Of the 200,902 pregnancies with pregnancy-induced high blood pressure, 166 had sleep apnea.

"The repetitive decrease in oxygen that occurs during the night in someone with sleep apnea heightens the body's 'fight or flight' state, which can raise blood pressure," explains researcher Hatim Youssef, D.O. of UMDNJ-Robert Wood Johnson Medical School. "The body also secretes more hormones such as cortisol and epinephrine, and the body responds by producing more glucose coupled with a decreased sensitivity to insulin, which can lead to diabetes."

Pregnancy can worsen sleep apnea, especially during the third trimester when a woman's weight is greatest, Dr. Youssef explains. "When a mother's oxygen level drops at night, it may also affect the oxygen level of the fetus, and we don't know what the long-term effects are. That's why it's important for a pregnant woman with sleep apnea to be treated with CPAP during her pregnancy."

It is not yet known whether CPAP treatment can reduce the risk of diabetes and hypertension during pregnancy, he says. "In the non-pregnant population, research has shown that treating sleep apnea will reduce the risk of diabetes and hypertension. In the future, we want to follow pregnant women whose sleep apnea is well-controlled to see if treatment prevents them from developing these conditions, or makes it less severe."

He recommended that pregnant women who are obese, hypertensive or diabetic be closely evaluated for the presence of sleep apnea.

If sleep apnea is present, treatment in the form of nasal CPAP should be used and her blood pressure and blood sugar should be closely monitored, Dr. Youssef says.